Laser-induced forward transfer-assisted flip-chip bonding of optoelectronic components

We report the Laser-Induced Forward Transfer (LIFT) of micro-bumps of silver nanoparticle and solder based paste for flip-chip bonding of single VCSEL chips. The electrical characterization results of the bonded chips are also presented

Active and passive component embedding into low-cost plastic substrates aimed at smart system applications

The technology development for a low-cost, roll-to-roll compatible chip embedding process is described in this paper. Target applications are intelligent labels and disposable sensor patches. Two generations of the technology are depicted. In the first version of the embedding technology, the chips are embedded in an adhesive layer between a copper foil and a PET film. While this results in a very thin (< 200 µm) and flexible system, the single-layer routing and the incompatibility with passive components restricts the application of this first generation. The double-sided circuitry embedding technology is an extension of the single-sided, foil-based chip embedding, where the PET film is replaced by a second metal foil. To obtain sufficient mechanical strength and to further reduce cost, the adhesive film is replaced by a substrate material which is compatible with the chip embedding concept. Both versions of the foil-based embedding technology are very versatile, as they are compatible with a broad range of polymer materials, for which the specifications can be tuned to the final application

An approach to produce a stack of photo definable polyimide based flat UTCPs

Getting output of multiple chips within the volume of a single chip is the driving force behind development of this novel 3D integration technology which has a broad range of industrial and medical electronic applications. This can be achieved by laminating multiple layers of spin-on polyimide based ultrathin chip packages (UTCPs) with fine pitch through hole interconnects

Technology development for a low-cost, roll-to-roll chip embedding solution based on PET foils

The aim of the research described in this paper is to develop a low-cost, roll-to-roll compatible process for the realization of electronic systems in foil using chip embedding. The small cost makes these systems suitable for disposable applications as food labels, medicine packages or smart bandages. Surface mount attaching of components on foils is a well-known process for building systems-in-foil. When using low-cost films like PEN and PET, there are serious restrictions on the maximum temperatures that can be used for the surface mounting process (soldering, adhesive bonding). Surface mounting has the additional disadvantage that the components are on the surface of the foil and are therefore not well protected mechanically and physically. The proposed process flow for embedding thin chips in PET foils overcomes these limitations. A key aspect of this technology is the application of a suitable adhesive to encapsulate the chips. The resulting product is based on full-metal copper which has a good thermal and electrical conductivity and allows for fine pitches. The process is compatible with several metal foils (Cu, Al …), offering further possibilities in cost reduction, and does not rely on bumping of the chips or plating of the interconnections to the chips

ENOBIO - First Tests of a Dry Electrophysiology Electrode Using Carbon Nanotubes

We describe the development and first tests of ENOBIO, a dry electrode sensor concept for biopotential applications. In the proposed electrodes the tip of the electrode is covered with a forest of multi-walled Carbon Nanotubes (CNTs) that can be coated with Ag/AgCl to provide ionic–electronic transduction. The CNT brushlike structure is to penetrate the outer layers of the skin improving electrical contact as well as increase the contact surface area. In this paper we report the results of the first tests of this concept—immersion on saline solution and pig skin signal detection. These indicate performance on a par with state of the art researchoriented wet electrodes.</p

Ultra-thin biocompatible implantable chip for bidirectional communication with peripheral nerves

To realize optimal recording and stimulation of peripheral nerve cells, a CMOS chip is made with a multitude of electrodes which can be individually addressed in order to select after implantation the 16 best positioned electrodes. Since the Foreign Body Reaction should be minimal for optimum electrode-nerve contact, the CMOS chip is thinned down to 35um and fully packaged resulting in a 75um thin encapsulated chip. The chip is embedded in a biocompatible stack consisting of polymers and inorganic diffusion barriers deposited using atomic layer deposition (ALD). A biocompatible metallization is realized using gold and platinum sandwiched between polymers and ALD layers for flexible interconnects, and iridium oxide (IrOx) is selected as electrode material for optimal charge injection during stimulation. After this dedicated packaging based on the FITEP technology platform (Flexible Implantable Thin Electronic Package), the CMOS chip is still fully functional, which was tested dry (in air) as well as during submersion in saline. The form factor of the packaged chip is optimized for intra-fascicular implantation with minimum tissue damage. First acute in vivo stimulation tests proved that the stimulation capabilities of the IrOx electrodes are very good

Interconnecting drivers to flexible displays

Several options to interconnect driver chips to a flexible display are discussed and investigated. In the first option, bare test dies are flip-chip (FC) assembled onto polyethylene terephthalate ( PET) display substrates. The second option involves test flexible polyimide ( PI) substrates, imitating tape-carrier-packaged drivers (TCP), bonded onto the same PET substrates, whereas the third option uses actual TCPs on stainless-steel display substrates. Each option makes use of bonding technology with anisotropically conductive adhesive, supplied as film (ACF). The reason for using ACF is that drivers typically have high output counts, and therefore very fine pad features, 200-mu m pitch and below. The technology has been adapted for each option, considering the requirements of the substrate. Every option includes an explanation of the bond test setup, the bonding process itself, and a discussion of the test results. The conclusion summarizes the achievements made in the research reported in this article