Novel interconnect methodologies for ultra-thin chips on foils

Lee

Int J Adv Manuf Technol

et al. 2015

A hybrid process including roll-to-roll (R2R) gravure printing, via-hole printing, and electroless plating was investigated for the creation of a double-side flexible printed circuit board (FPCB). A R2R gravure process with an Ag seed layer that includes front-and back-side printing with a polyimide film at the center was investigated. The gravure-printed Ag pattern was laser drilled for high accuracy. A via hole was filled with a low-viscosity Ag ink using the drop-casting method. In addition, an electroless Cu plating process was performed to increase the conductivity of the printed circuit. The interconnection performance was confirmed from the resistance values obtained using a feed-through test and microscopic images. To evaluate the reliability of the FPCB, a cyclic bending motion test was performed; stable electrical performance was observed even after 400,000 cycles. The results obtained in this study suggest that the proposed hybrid process for double-side FPCBs is viable for a mass production system.

Section: Double-side Printingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Development of hybrid process for double-side flexible printed circuit boards using roll-to-roll gravure printing, via-hole printing, and electroless plating

Lee

Int J Adv Manuf Technol

et al. 2015

2012 4th Electronic System-Integration Technology Conference

“…Based on earlier investigations [1], the laser scribing of conductive patch was selected as the method to create via metallization and interconnection. The investigations showed that this method offers key advantages over other candidate technologies for via metallization and interconnection, viz.…”

Section: Process Selection For Demonstrator Fabricationmentioning

confidence: 99%

“…Examples of such products are lighting and signage devices, displays, wearable electronic products etc. [1] The additive nature of printing processes, their maturity, high throughput and compatibility with both roll-to-roll (R2R) and sheet-to-sheet (S2S) fabrication are some of the factors that make printed electronics suitable for low-cost large-area electronics. However, printed electronics by itself cannot cater to all the requirements of a large-area electronic system.…”

Section: Introductionmentioning

confidence: 99%

Novel methodology to integrate ultra-thin chips on flexible foils

Sridhar

Cauwe²,

Kusters

et al. 2012

Self Cite

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.

2012 4th Electronic System-Integration Technology Conference

“…100 cycles. The samples were flexed on cylinders with progressively decreasing bending radius (see [8] for details of the test). The LEDs were tested at a fixed point while strained around the cylinder.…”

Section: Methodsmentioning

confidence: 99%

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

Ende

Kusters

Cauwe³

et al. 2012

Self Cite

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 (<100ºC 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.