Silicon validation is a process of identifying failures resulting from testing during silicon bring-up. During the IC design and manufacturing cycle, manufacturing tests screen out the failed chips. Diagnosis is done to find out why the chips failed, which becomes especially important when the yield is low or when a customer returns a failed chip. With shrinking technology nodes, new types of physical defects arise. This fact makes the diagnostic process quite tricky, difficult, and timeconsuming. This article will cover different challenges one faces during silicon debug, and guidelines to be followed to enable faster and more effective diagnosis for ATPG scan test.