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

Flip-chip bonding of fine-pitch ultra-thin chips for SiF applications

This paper describes the successful process investigations on ultrathin flip-chip bonding for fine-pitch applications on foil, using a novel bonding process involving Isotropic Conductive Adhesives (ICA). A Ag-based B-stage curing ICA was printed using state-of-the-art electroformed stencil on printed Ag circuitry, pre-cured and flip-chip bonded at low bonding force and short duration. The interconnection resistance measurements, performed before and after a stabilizing underfilling step, revealed low interconnect resistances down to 150 μm bond pad pitch. Finally, the reliability of the specimens prepared using this process was successfully evaluated by means of standard reliability test procedures such as thermal shock testing and accelerated humidity testing

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

Bonding bare die LEDs on PET foils for lighting applications: thermal design modeling and bonding experiments

Integration of LEDs on flexible foil substrates is of interest for flexible lighting applications and flexible photonic devices. A matrix of LEDs on a foil combined with a diffuser can be a potential alternative for flexible OLED lighting devices. Preferably, these LEDs are integrated in an unpackaged, bare die form as it reduces cost, footprint and thickness. As a substrate, preferably low cost materials like polyesters (PET) are being used, especially for large area devices. However, the use of these materials imposes some limitations. Most notably, the low temperature stability (<100 degrees C continuous use temperature) of these materials limits the maximum temperatures during the manufacturing process and poses constraints on the thermal design of the device. The current paper describes the results of research on possibilities for integrating bare die LEDs with low cost flexible PET foils. Finite element (FE) thermal modeling has been performed of possible designs of adhesively bonded LED-on-foil and laminated LED-in-foil configurations. The role of the different materials and the effect of their geometries on the temperature distribution in the simulated devices are discussed. The results give insight in measures that can be taken to keep the temperature of all the components of the device within operational limits. For LEDs bonded on Cu-PET foil the modeled temperature distributions are compared to experimentally observed temperature distributions in LED on PET foil reference devices using infrared thermal imaging. Besides this, initial studies on directly bonding LEDs on etched Cu on PET substrates using anisotropic conducting adhesives and isotropic conducting adhesives were performed. An experimental comparison is made between the different techniques based on temperature/humidity reliability and flexural stability of the bonded LEDs, based on these preliminary results

A conformable active matrix LED display

Conformable and stretchable displays can be integrated on complex surfaces. Such a display can assume the shape of a conformed surface by simultaneous multi-dimensional stretching and bending. Such technology provides new opportunities in the field of display applications, for example wearable displays integrated or embedded in a textile or onto complex surfaces in automotive interiors. In this work we present a conformable active matrix display using LEDs mounted on an amorphous Indium-Gallium-Zinc Oxide (a-IGZO) TFT backplane. A two-transistor and one capacitor (2T-1C) pixel engine based backplane, fabricated on polyimide substrate, is used to drive LEDs. Rigid LED pixels are connected via meandered copper film. The meander interconnections have been optimized with respect to their electrical and mechanical properties to provide a display with a 2 mm pitch between the pixels and good conformability. At an operating supply voltage of 7 V, the average brightness of the display exceeds 170 cd/m2

Stoma-free survival after anastomotic leak following rectal cancer resection : worldwide cohort of 2470 patients

Funding Information: The TENTACLE-Rectum study was funded by Medtronic External Research Program. The authors declare no other conflict of interest.Peer reviewedPublisher PD

Post-Operative Functional Outcomes in Early Age Onset Rectal Cancer

Background: Impairment of bowel, urogenital and fertility-related function in patients treated for rectal cancer is common. While the rate of rectal cancer in the young (&lt;50 years) is rising, there is little data on functional outcomes in this group. Methods: The REACCT international collaborative database was reviewed and data on eligible patients analysed. Inclusion criteria comprised patients with a histologically confirmed rectal cancer, &lt;50 years of age at time of diagnosis and with documented follow-up including functional outcomes. Results: A total of 1428 (n=1428) patients met the eligibility criteria and were included in the final analysis. Metastatic disease was present at diagnosis in 13%. Of these, 40% received neoadjuvant therapy and 50% adjuvant chemotherapy. The incidence of post-operative major morbidity was 10%. A defunctioning stoma was placed for 621 patients (43%); 534 of these proceeded to elective restoration of bowel continuity. The median follow-up time was 42 months. Of this cohort, a total of 415 (29%) reported persistent impairment of functional outcomes, the most frequent of which was bowel dysfunction (16%), followed by bladder dysfunction (7%), sexual dysfunction (4.5%) and infertility (1%). Conclusion: A substantial proportion of patients with early-onset rectal cancer who undergo surgery report persistent impairment of functional status. Patients should be involved in the discussion regarding their treatment options and potential impact on quality of life. Functional outcomes should be routinely recorded as part of follow up alongside oncological parameters

Novel methodology to integrate ultra-thin chips on flexible foils

The placement and integration of ultra-thin chips (UTCs) on low-cost polymer foils is a key challenge in the realization of large-area flexible electronic products. Such products, are for cost reasons, preferably fabricated on low cost polyester foils like PET/PEN. A disadvantage of these materials is that they have a low thermal stability. As a consequence of this, the majority of existing chip integration technologies cannot be used. A novel approach for placement and interconnection of UTCs is presented in this paper. This approach, which involves face-up bonding of UTC and its subsequent interconnection, is compatible with low-cost polymer foils. The key process steps involved in UTC integration using the proposed methodology are discussed in detail. The fabrication of a technology demonstrator to validate the proposed concept is also detailed

Integration techniques and applications of thin chips on low cost foil substrates

Large area flexible foil based electronic products are expected to be used in a wide range of applications and in large quantities in our society. Examples of this include sensor systems integrated into food packaging or healthcare and sport monitoring tags as wearable patches or in clothing. Intelligence and communicative capabilities are preferably added to these devices by integrating chips and passives directly on the foil itself. To maintain low thickness and therefore flexibility of these systems, thinned bare die chips, thin passives and unpackaged LEDs are used. For cost effectiveness the preferred substrate material for these large area systems will be low cost polyester materials such as PET (polyethylene teraphtalate) foils. The low thermal stability of the PET foils however puts serious constraints on the integration process and materials, rendering many conventional integration technologies unfeasible. In this paper, several integration techniques are presented that are compatible with low cost foils. These include low temperature flip chip bonding on PET foil substrates, chip embedding in flexible polyurethane boards and a novel face up chip integration technique. This face up chip integration technique is compatible with low cost PET foil processing and screen printing techniques. To attest the extreme flexibility of these systems, flexural strength results of ultrathin silicon dies are presented as well as lifetime and flexural test results of these chips integrated on foil substrates. Application examples of thin-chip integration are presented in the form of a supply chain monitoring tag, a smart label and a flexible lighting sheet of bare die LEDs on Cu-PET foil. These functional demonstrators consist of an integrated bare die microcontroller and LED chips on low cost foil substrates using flip chip technologies and integration of bare die microcontrollers and passives using double sided embedding techniques in polyurethane flexible substrates