The acceptable flexibility for ultra-thin substrate would be reached by embedding the ultra-thin substrate into the flexible polyimide and patterning the poly-silicon or silicon into square/hexagon segmentations. The segments interconnect by metal wires for the signal communication, different wire shapes are designed to reach more flexible. In this contributions, results of FE optimization on mechanical reliability issues of interconnect in-between segments on ultra-thin polyimide/silica rubber substrates are presented. Generation of cracks within the silicon and dielectric layers is then studied under controlled bending (glass cylinders with diameters of 2 - 10 mm, compressive and tensile stress) using specially for this purpose designed bending tools. Specimen observation is done using an optical microscope with possibility of digital recording and evaluation by pattern recognition software. The results show that the cracks appear first in the dielectric layers in-between the silicon layer segments and only at higher loads propagate or are generated within the silicon itself. The development of first cracks depends significantly on the silicon layer segmentation size which affects both the crack density and the crack width. The crack density increases sharply with the strain for early stage and then increases slightly. The crack width increases steadily. The high flexibility result can be reached that no crack be detectd under the bending tests with 2 mm diameters. Multilevel FEM simulations are performed in order to increase understanding of the major failure processes. Results of simulations and experiments compare quite well. Second generation samples are designed with consideration of interconnect in-between segments and avoid of silicon dioxide in-between segments.@en

This paper reports on fabrication and design considerations of an integrated folded shorted-patch chip-size antenna for applications in short-range wireless microsystems and operating inside the 5¿6 GHz ISM band. Antenna fabrication is based on wafer-level chip-scale packaging (WLCSP) techniques and consists of two adhesively bonded glass wafers with patterned metallization and through-wafer electrical interconnects. Via formation in glass substrates is identified as the key fabrication step. Various options for via formation are compared and from these, a 193 nm excimer laser ablation is selected for fabrication of the antenna demonstrator. The fabricated antenna has dimensions of 4 mm × 4 mm × 1 mm, measured operating frequency of 5.05 GHz with a bandwidth of 200 MHz at the return loss of ¿10 dB and a simulated radiation efficiency of 60% were achieved. Keywords: Chip-size antenna; Wafer-level packaging; Wireless microsystem; Excimer laser ablation; Via fabrication@en

This paper reports on an area-selective adhesive wafer bonding, using photosensitive BCB from Dow Co. The strength of the fabricated bonds is characterized using the wedge-opening and tensile methods. The measured fracture toughness is 53.5±3.9 J/m2 with tensile strength up to 71 MPa. The potential application of BCB bonding is demonstrated on a concept of wafer-level chip-scale package for RF applications and microfilter array for microfluidic applications. ©2005 ASME@en