  A geometric construction is provided that associates to a given flat front in
$\mathbb{H}^3$ a pair of minimal surfaces in $\mathbb{R}^3$ which are related
by a Ribaucour transformation. This construction is generalized associating to
a given frontal in $\mathbb{H}^3$ , a pair of frontals in $\mathbb{R}^3$ that
are envelopes of a smooth congruence of spheres. The theory of Ribaucour
transformations for minimal surfaces is reformulated in terms of a complex
Riccati ordinary differential equation for a holomorphic function. This enables
one to simplify and extend the classical theory, that in principle only works
for umbilic free and simply connected surfaces, to surfaces with umbilic points
and non trivial topology. Explicit examples are included.
