  An integer is said to be $y$-friable if its greatest prime factor is less
than $y$. In this paper, we obtain estimates for exponential sums over
$y$-friable numbers up to $x$ which are non-trivial when $y \geq \exp\{c
\sqrt{\log x} \log \log x\}$. As a consequence, we obtain an asymptotic formula
for the number of $y$-friable solutions to the equation $a+b=c$ which is valid
unconditionnally under the same assumption. We use a contour integration
argument based on the saddle point method, as developped in the context of
friable numbers by Hildebrand & Tenenbaum, and used by Lagarias, Soundararajan
and Harper to study exponential and character sums over friable numbers.
