Secure key establishment in wireless sensor networks has been shown to be efficient. For sake of computation power, pre- distribution of symmetric keys is recommended. In such schemes, a set S of keys is used and each deployed node knows a subset of S. However, the capture of nodes can quickly lead to the corruption of a significant part of the network and solutions like multi-deployment have been proposed. In multi-deployment schemes, sets of nodes – using different key sets – are sequentially deployed that limits the impact of the capture of nodes. In this paper, we consider the problem of connectivity of single deployment in regards to the size of key sets. We show that connectivity guaranteed solutions lead to network vulnerability when nodes are captured. Then we evaluate network robustness of different schemes.