This paper shows how common embroidery can be used to integrate electronics into textile environment in a light and cost efficient way. A mechanism has been developed to embroider through flexible electronic modules using conductive yarn, thus creating an interconnection with other modules like sensors, batteries, textile keyboards, etc. Mold encapsulation has been found to improve the electrical contact and support the reliability of the whole system.
A packaging process for flip-chip LEDs (light emitting diodes) is described. The LEDs are picked and placed on a silicon substrate wafer. After reflow the substrates are individualized. AuSn solder is used for the interconnection. The solder compounds, Au and Sn, are electroplated separately: Sn on the silicon substrate and Au on the chip. The interconnections formed by tin-rich and by gold-rich intermetallic phases are compared. The metallurgy and the reliability of the LEDs are investigated. The superiority of the gold-rich interconnection is demonstrated.
Ultra thin silicon ICs with a remaining thickness of less than 30 µm are investigated with respect to their manufacturing technology and mechanical behavior. Thin wafers which were diced using a standard sawing process reveal low fracture resistance when a bending force is applied to single chips. To eliminate influence of micro-cracks induced by sawing extremely thin wafers, the new concept "Dicing by Thinning" was developed and is explained in the paper. The concept allows manufacturing of 10 - 30 µm thin wafers and includes self-acting die separation during thinning procedure. Best results are achieved when dicing lines between chips are prepared at front side of wafer by dry etching methods. First results of analysing mechanical reliability of thin silicon samples are presented and discussed
Passive transponder labels are available in a variety of types mainly for logistic purposes which require higher functionality and/or higher reliability than the conventional barcodes allow.Smart labels for textiles either for production, logistics or professional laundry have to meet different requirements from these applications. They have to be ultrathin and very reliable under conditions unusual for electronics (washing, high pressure,. . .). Therefore the realization of textile transponders has become possible only recently with the development of thin silicon chips. Such chips are flexible and can overcome high mechanical load. They can he easily encapsulated and can resist the extreme conditions of a washing process.In order to achieve high readout distances (0.5 ... 2 m) the antennas have to enclose an area of > 6 an2, The reliability of flexible substrates in this size during washing procedures is not suficient. Therefore textile based antennas have to be produced. The transponder IC's have to he assembled to conductive yarn. The module also needs encapsulation to protect the IC from humidity, chemicals etc.. This requires new technologies especially as the dimensions and tolerances between microelectronic components and textiles differ by orders of magnitude. The development of these technologies will be the hasis for the realization of textile based wearable electronic assistants which will be a key component of future ubiquitous computing. This paper presents a concept to realize textile based transponders, the electrical interconnections to conductive yarn and first experimental results.
Commonplace electronic appliances for consumer or industrial use are still mostly rigid or at maximum flexible entities. The flexibility of foldable units like laptops or cell phones is usually realized through flexible circuit board (FCB) interconnectors. Although flexibility allows for considerably enhanced degrees of freedom in design, it is not compatible with more complex three dimensional curvatures and dynamics thereof. In the past years a number or approaches to realize stretchable electronic circuits in order to reach beyond unidirectional bending or folding of electronics have been reported. In the frame of the European Project STELLA a particular fabrication technology for stretchable electronic systems has been developed at Technische Universitaet Berlin. This technology, termed "stretchable circuit board" (SCB) technology, is derived from conventional printed circuit board manufacturing. Stretchability of the boards is enabled by (i) using polyurethane inst ead of FR4 or polyimide as a carrier material of the copper structures and (ii) a meandering design of the Cu interconnects between commercial (rigid) electronic components. Such boards can be (once) extended by up to 300 % before fracture of the Cu interconnections. For repeated elongation/relaxation cycles elongations with a few percent are allowable in order reach high cycle numbers. Electronic components are assembled after local application of a solder mask and surface finish for solderability. The electronic interconnection is established using a low temperature solder alloy (SnBi, Tm=142 °C). For protection and enhanced system robustness all components are subsequently encapsulated within a polyurethane capping. Systems thus realized can be readily attached to different kinds of surfaces. Most interesting for various application cases is the easy attachment to textile substrates by a simple lamination process. The field use case studies of stretchable systems in the frame of the STELLA are m
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