The adhesion between the electroless seed layer and the buildup film substrates was studied. After the buildup film was laminated, the buildup film surface was modified by a desmear treatment from 0 to 30 min, and electroless Cu or electroless Ni-P was plated as the seed layer on the buildup film. The Cu was then electroplated, and the post curing was carried out at 180 • C for 2 h before or after Cu electroplating. The adhesion strength between the electroless seed layers and the buildup film substrates was measured by the 90 • peel test. Increasing the desmear treatment time made the buildup film surface rougher, and consequently enhanced the adhesion strength of the electroless Cu and electroless Ni-P to the film. Under the same conditions, the electroless Ni-P specimen showed a higher peel strength than the electroless Cu specimens. Post curing significantly increased the adhesion strength due to the increased ductility of the metal layer after heat-treatment. In addition, the peel strength decreased as the thickness of the seed layer increased, which was also related to the mechanical properties of each metal layer.Electroless metallization is widely used for the fabrication of circuit patterns in microelectronics because electroless plating can deposit on wide variety of materials including insulating surfaces such as glass, oxides, and polymers, without the need for any electrical equipment. 1,2 However, the electroless plating of metal on polymer substrates is often limited by weak adhesion strength caused by structural incompatibility between the substrate and the metal layer. The finer dimensions of the typical interconnection pattern obtained from the buildup film has made even the reliability of packages critical; therefore, good adhesion of the metal on the buildup insulating films is essential. 3,4 Cu metal has been widely used in semiconductor manufacturing due to its high conductivity and low cost, 5,6 and electroless copper is usually deposited on the buildup insulating film as a conducted seed layer for subsequent Cu electroplating. In order to improve the adhesion of plated copper on the polymer film, many processes involving plasma activation followed by surface graft polymerization have been carried out. 7,8 However, compared to plasma processes wet chemical treatments are preferred industrially due to the much lower cost. 3,9 A typical wet chemical processes for the pretreatment of buildup film consist of three steps: swelling, desmear and neutralization. 10 After pretreatment, mechanical interlocks that utilize anchoring sites on the roughened surface of the buildup insulating film enhance adhesion. 3,9,10 Electroless nickel has also been studied as a potential conducted seed layer deposited on buildup film for Cu electroplating. 8,11 However, even though many techniques has been developed to enhance the adhesion of the metal layer to the insulating substrate, previous research has mainly focused on the interfacial energy effect such as chemical bonding. However, the mechanical effect of th...
This study aims to understand the street-crossing-facility choice behavior of the elderly. The footbridges were classified into three types with different levels of convenience. On the other hand, the safety of the crosswalk was assumed to be highly related to the remaining time of pedestrian green light. An adaptive SP survey was designed to collect choice data from individuals aged 60 years or above, and a multilevel logistic model was developed to analyze the behavior data. The results indicated that convenience and safety exert significant influence on the facility choice behavior. The choice behavior of the elderly toward making trade-off decision between convenience and safety was further discussed through the multilevel logistic regression analyses.
A semi-active wavelength division multiplexing (WDM) system based on pilot-tone relay detection is proposed and experimentally demonstrated for 5G centralized front-haul network, which is composed of a passive WDM multiplexer at active antenna unit (AAU) side, an active WDM equipment at distributed unit (DU) side, and several WDM optical modules in AAU and DU, respectively. In this semiactive WDM scheme, WDM technology is applied as an optical transport layer to save fibers and the semiactive architecture based on pilot-tone modulation is capable of flexible deployment with lite operation, administration and maintenance (OAM) functions. The experimental results show that the sensitivity penalty is lower than 0.3 dB and the extinction ratio is still higher than 4.2 dB by using 4 % amplitude depth of pilot-tone modulation. The bit rate of the OAM signal is 1024 bps to reuse the existing microcontroller unit in the optical modules for generating and detecting OAM signals. The robustness of the pilot-tone signals is further demonstrated as the sensitivities of the 25-Gbps eCPRI signals and the 1024-bps OAM signals are -16 dBm and -23 dBm, respectively. Compared with the OAM demodulation both in upstream and downstream direction for the active WDM equipment, the number of OAM demodulation unit can be reduced by 50% and the sensitivity requirement of OAM demodulation can be improved by 11.5 dB by using only downstream OAM demodulation unit. Error-free 24-hour transmission of real-time 12-channel 25-Gbps eCPRI signals combined with 1024-bps pilot-tone OAM signals over 10-km single mode fiber is obtained.
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