An interposer for evaluating an electrical characteristic of a ball grid array package or of a semiconductor die thereof. The interposer includes electrically conductive vias positioned correspondingly to bond pads of the semiconductor die and to the electrical contacts or terminals of a carrier substrate of the ball grid array package. Test pads, or contact pads, are disposed proximate an outer periphery of the interposer. Each of the test pads is in electrical communication, preferably by means of electrical traces, with a corresponding electrically conductive via of the interposer. In use, the interposer is aligned with and disposed between the semiconductor die and the carrier substrate such that the test pads of the interposer are at least partially located outside of a periphery of the semiconductor die. Thus, the test pads are exposed around the ball grid array semiconductor die and are, therefore, accessible to electrical testing equipment. Upon contacting a test pad of the interposer with a probe operatively associated with electrical testing equipment, an electrical characteristic of the ball grid array package or the semiconductor die thereof may be evaluated. The present invention also includes assemblies of any combination of a semiconductor die, a test interposer, and a carrier substrate. Accordingly, the invention also includes a ball grid array package comprising a ball grid array semiconductor die, a test interposer, and a carrier substrate. The invention also includes methods of designing the interposer, as well as assemblies and ball grid array packages including the interposer.