Flip-chip device strengthened by substrate metal ring

Electronic devices of improved reliability having a substrate of electrically insulating material, further an integrated circuit chip with a periphery and a surface. Using a layer of polymeric material, the chip surface is mounted on the substrate surface. The polymeric material protrudes beyond the chip periphery and spreads some distance along the substrate surface. A metal layer is on the substrate surface, this layer is shaped as a band around the chip periphery; the band has an inner edge near the chip periphery, and an outer edge near the contour of the polymer protrusion. This metal band serves as a guard ring to stop any nascent crack propagating in the polymer protrusion.