A structure. The structure includes: a first dielectric layer which includes a top dielectric surface; an electrically conductive line on the first dielectric layer; a second dielectric layer on the first dielectric layer and the electrically conductive line; a ball-limiting-metallurgy (BLM) region on the second dielectric layer and the electrically conductive line such that the BLM region is electrically connected to the electrically conductive line; and a solder ball on the BLM region. The BLM region has a characteristic that a length of the longest straight line segment which is parallel to the top dielectric surface and is entirely in the BLM region does not exceed a pre-specified maximum value, wherein the pre-specified maximum value is at most one-half of a maximum horizontal dimension of the BLM region measured in a horizontal direction parallel to the top dielectric surface.