Kostas Papathomas

Encapsulant for fatigue life enhancement of controlled-collapse chip connection (C4)

Controlled collapse chip connection (C4), or flip chip connection, has been used since late 1960s as a reliable interconnection technology for semiconductors. Allowing area array type of interconnection, this method provides one of the best solutions for high density packaging. However, with trends migrating to larger DNP (distance to neutral point) chips and organic substrates, the fatigue life of solder joints need to be enhanced by encapsulation. To meet the stringent requirements of flip-chip encapsulation, low viscosity resins based on epoxy chemistry have been developed by IBM. These systems having low thermal expansion, low /spl alpha/-particle emission, excellent flow, and wetting characteristics can provide improved mechanical and environmental protection of the solder joints. This article describes the characterization of a liquid, silica filled system for maximum processability of C4 chips. Critical thermomechanical properties have been studied to ensure that both ceramic module and card assembly conditions can be sustained. Both rheological properties and cure kinetics were optimized to provide enhanced flow and coverage of the C4s. Other key properties such as, shelf life, thermal stability, solvent and moisture resistance as well as adhesion to various surfaces are addressed. >

Cure monitoring of a photosensitive polymer using the luminescent organometallic complex fac-CIRe(CO)3(4,7-Ph2-phen)

Abstract The organometallic complex fac-CIRe(CO)3(4,7-Ph2-phen) exhibits a bright yellow-orange phosphorescence centred at 576 nm in poly(methyl methacrylate)/trimethylolpropane triacrylate (PMMA/TMPTA) solutions. This luminescence feature is shown to be a useful spectroscopic probe of the acrylate crosslinking reactions in the u.v. photochemical curing of a model PMMA/TMPTA thin film system.

Low Dielectric Constant Laminates Containing Microspheres

As electronic devices become faster, the effective dielectric constant of the circuit packaging connecting them becomes more important. The dielectric constant of standard epoxy/glass laminates can be significantly reduced by the addition of hollow glass microspheres. However the addition of such microspheres usually results in the degradation of other physical, electrical and mechanical properties which are prerequisites for materials to be used in commercial circuit packaging. By carefully optimizing the formulation many of these undesirable effects can be avoided. These topics and others pertaining to the development and testing of a microsphere laminate are discussed.

Development of conductive adhesive materials for via fill applications

As mobile computing and telecommunication electronics are spreading fast, a demand for microelectronics packaging schemes for high density, fine pitch, high performance and low cost becomes even more severe. Specifically, the conventional printed circuit board (PCB) with plated-through-hole (PTH) vias is difficult to justify its manufacturing cost as well as the packaging density requirement. To meet this challenge, several new manufacturing schemes of high density and high performance PCB have been recently introduced such as surface laminar circuit (SLC), array layer inner via hole (ALIVH) and others. This new PCB fabrication process is categorized as sequential build-up (SBU) or build-up multilayer (BUM) using laminate-based substrates, where via holes are filled with a conductive paste material to make reliable vertical or Z-interconnects. In this paper, a new electrically conducting paste material to be used for via filling is introduced. The new conducting material consists of a conducting filler powder coated with a low melting point metal or alloy, a mixture of several thermoset resins, and other minor organic additives. By varying the filler content and resin chemistry, several formulations have been produced to fill via holes with a high aspect ratio. Via fill experiments have been performed to demonstrate void-free microstructure with good electrical continuity. Various bulk properties such as thermal, electrical and mechanical have also been characterized to understand the material behavior during via filling as well as the field service.

iNEMI BFR-free PCB materials evaluation project report

Brominated flame retardants, namely polybrominated diphenyl ethers (PBDEs), were one of the main materials used to reduce the flammability of consumer goods and electronics. Growing evidence shows that PBDE compounds are making their way into the environment. These chemicals may cause health effects, prompting many nations to ban or suspend their use in new consumer goods.