Contact Resistance Characteristics of Elastomeric Complex Structure Contacts for Gold and Tin Printed Circuit Board
Characteristics of conductive elastomer which is composed of silicone rubber and dispersed carbon black particles shows conductive and elastic properties in one simple material. This material has been widely applied to contacts of switches and connectors of a liquid crystal panels. However, since surface state of the contact is very soft, it is difficult to remove contaminant films of contaminated opposite side contact surface and to obtain low contact resistance owing to break the film. This study has been conducted to clear structures of the elastomer which indicates removal characteristics for contaminant films and low contact resistance. As specimens, six different types of the elastomer contacts composed by different type of dispersed such materials as carbon and metal fibers, metal mesh, and plated surfaces were used. The opposite contacts were Au and Sn plated contact surface on a printed circuit board (PCB). The elastomeric contacts contained hard materials showed lower contact resistance than only dispersed carbon particles in the elastomer matrix for both contaminated PCB contact surfaces.
Contact Resistance Characteristics of Improved Conductive Elastomer Contacts for Contaminated Printed Circuit Board in SO2 Environment
Characteristics of conductive elastomer that is composed of silicone rubber and dispersed carbon black particles show conductive and elastic properties in one simple material. This material has been widely applied to make-break contacts of panel switches and connectors of liquid crystal panels. However, since surface state of the contact is very soft, it is difficult to remove contaminant films of contaminated opposite side contact surface and to obtain low contact resistance owing to break the film. This is an important problem to be solved not only for the application of make-break switching contact but also static connector contacts. This study has been conducted to examine some complex structures of the elastomer which indicate removal characteristics for contaminant films and low contact resistance. As specimens, six different types of elastomer contacts composed of different type of dispersed materials as carbon and metal fibers, metal mesh, and plated surfaces were used. The contacts of opposite side were Au and Sn plated contact surface on a printed circuit board (PCB) which is usually used in the static connector and make-break contacts. In order to contaminate contact surfaces of PCB, the surfaces were subjected to exposure in an SO 2 gas environment. The elastomeric contacts contained hard materials showed lower contact resistance than only dispersed carbon particles in the elastomer matrix for both contaminated PCB contact surfaces.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.