Experimental study of PCB gold connectors defaults and implementation of diagnostic tools

This work has for objective the study of the fault leading to the failure of insertable gold-plated connectors. Several factors can be at origin of a 'false contact' in this kind of connector: loss of force due to the relaxation of springs, corrosion and pollution. If solutions have been brought to protect against the corrosion (gold deposit in contact areas), loss of the mechanical properties of the contacts is inevitable due to their long planned life (40 years initially). Their remaining life expectancy represents a major issue and needs to be known. To answer this, the evolution of various parameters that characterize these connectors, such as insertion force, contact force, springs deflection, and contact resistance, has been studied for a high number of operations of insertion/withdrawal phases thanks to insertion and friction contacts benches that have been developed. EDX Analysis of the contact areas was performed to estimate the extent of contact surface damage. Once these parameters were known, an innovative prototype sensor for force measurement was developed for the connector, based on the piezoresistive effect that allows direct measurement of contact force to be made. A major observation during the force measurements made with this sensor is variation of this parameter depending upon the contacts. The geometric tolerance of the connector housing is assumed to be the major explanation of these variations. A correlation is made between measurements obtained by force sensor and measurements of distances between springs (difference of gap) obtained thanks to a visual connector inspection system with the aim of finding a causal effect between those two parameters. (author)