An (r, w; d) cover-free family (CF F ) is a family of subsets of a finite set such that the intersection of any r members of the family contains at least d elements that are not in the union of any other w members. The minimum number of elements for which there exists an (r, w; d) − CF F with t blocks is denoted by N ((r, w; d), t).In this paper, we show that the value of N ((r, w; d), t) is equal to the dbiclique covering number of the bipartite graph I t (r, w) whose vertices are all w-and r-subsets of a t-element set, where a w-subset is adjacent to an rsubset if their intersection is empty. Next, we introduce some new bounds for N ((r, w; d), t). For instance, we show that for r ≥ w and r ≥ 2where c is a constant satisfies the well-known bound N ((r, 1; 1), t) ≥ c r 2 log r log t. Also, we determine the exact value of N ((r, w; d), t) for some values of d. Finally, we show that N ((1, 1; d), 4d − 1) = 4d − 1 whenever there exists a Hadamard matrix of order 4d.