Patent ID: 7232707

Claim:
A method of making a semiconductor chip assembly, comprising: providing a metal base, a trench, a routing line and a pillar etch mask, wherein the metal base includes first and second opposing surfaces, the trench extends into but not through the metal base from the second surface of the metal base towards the first surface of the metal base, is spaced from the first surface of the metal base and includes inner and outer peripheries that are adjacent to the second surface of the metal base, the inner periphery surrounds and is adjacent to a portion of the second surface of the metal base, the outer periphery surrounds and is spaced from the inner periphery, the routing line contacts the first surface of the metal base and is spaced from the trench, the pillar etch mask includes a metal layer and a solder layer, the metal layer contacts and covers the portion of the second surface of the metal base and extends into the trench, the solder layer contacts the metal layer, covers and is spaced from the portion of the second surface of the metal base and extends into the trench, and the metal layer and the solder layer form a flange that extends into the trench; mechanically attaching a semiconductor chip to the routing line, wherein the chip includes a conductive pad; forming a connection joint that electrically connects the routing line and the pad; etching the metal base using a wet chemical etch, thereby reducing contact area between the metal base and the routing line and forming a metal pillar from an unetched portion of the metal base that contacts the routing line, wherein a portion of the first surface of the metal base forms a pillar base of the metal pillar, the portion of the second surface of the metal base forms a pillar tip of the metal pillar, the wet chemical etch removes all of the metal base adjacent to the outer periphery, removes none of the metal base adjacent to the inner periphery and forms the pillar base, and the pillar etch mask protects the pillar tip from the wet chemical etch; and providing a contact terminal that is a permanent part of the assembly, wherein the contact terminal contacts and covers the pillar tip, includes the metal layer, the solder layer and the flange and includes a solder surface that faces away from the pillar tip and is exposed.