Due to ongoing miniaturization in electronics, connector contact designs
have to follow the same trends. The prediction of the mechanical and
electrical performance of low force connector contacts becomes increasingly
important. This paper shows a new approach for modeling elastic plastic
contact between two multi-layered non-conforming rough bodies subjected to
pressure and shear traction. Three main considerations will be presented:
realistic surface simulations, numerical simulation of contact interfaces,
and constriction resistance calculations. (i) Since measured three
dimensional (3D) digitized surface data is not always available, having the
ability to numerically simulate “realistic” rough surface topographies is of
great importance. It will be shown how realistic engineered surfaces can be
modeled using five scale independent parameters: RMS roughness, x/y
correlation length, kurtosis and skew. (ii) A numerical algorithm has been
developed which calculates the stresses and deformations generated in a
contact system with up to three different layers per contact partner. The
mechanical properties of each individual contact layer are incorporated into
the calculation. This numerical algorithm is based on Papkovich-Neuber
Potentials, both multi grid and conjugate gradient methods are used, and the
plastic deformation of the individual contact points (a-spots) can be
interpolated using different material hardening behaviors. (iii) Once the
contact interface a-spot distribution is simulated, the constriction
resistance of the true contact area can then be calculated. The voltage drop
within the contacting bodies is interpolated by iteratively solving the
Laplace equation. The electrical properties of all the individual contact
layers as well as the interaction between the individual a-spots are taken
into account. A validation of these simulation algorithms will be shown
using a hard Au/Ni/CuSn6 contact system. The results show excellent
agreement between measured and simulated contact resistance results over a
normal force range from 1 cN up to 250 cN. The algorithms have been
implemented with an “easy to use” Windows software interface called “First
Contact”. The software also incorporates a material database that when used
together with a surface modeler, allows for the fast calculation and 3D
visualization of all mechanical and electrical contact characteristics.