Patent ID: 6194782
Filing Date: 2001-02-27
Classification: H01L,H05K,Y02P

Abstract:
An integrated circuit package for mounting on a base substrate of local coefficient of thermal expansion .alpha..sub.3 comprising:a package substrate of local coefficient of thermal expansion .alpha..sub.pkg, the package substrate having conductive traces on a top surface interconnected by vias to conductive traces on a bottom surface of the package substrate;a semiconductor die mounted either on or adjacent a top surface of the package substrate and electrically connected to the conductive traces on the top surface of the package substrate;an array of conductive surface mount terminations of finite thickness mounted on a bottom surface of the package substrate at least some of which are electrically connected to the conductive traces on the bottom surface of the package substrate;the terminations being arranged in rings i around a neutral point of the package;each of the rings being a distance DNP.sub.i from the neutral point of the package;each of the rings having a number of terminations n.sub.i ;each ring having a termination pitch P;the terminations having a modulus of elasticity E.sub.t and a structural thickness h.sub.t ;the package having a modulus of elasticity E.sub.pkg and a structural thickness h.sub.pkg ;successive rings having a change in the distance from the neutral point of the package .DELTA.DNP;each of the rings cycling through a temperature range .DELTA.T.sub.i during operation; andat least one adhesive mass;the at least one adhesive mass being located on the bottom of the package substrate in the area(s) where the terminations when mounted upon the base substrate to form joints would have highest joint strain energy density W.sub.Gi as calculated by the equationsW.sub.Gi =k.sub.i {DNP.sub.i (.alpha..sub..beta. -.alpha..sub.pkg).sub.i.DELTA.T.sub.i }.sup.2k.sub.i =l/4n.sub.i.SIGMA.(1/.DELTA.K.sub.j).sub.j-1,i.DELTA.K.sub.j =(P/.DELTA.DNP).sub.j /{1/(Eh).sub.t +1/(Eh).sub.pkg }.sub.jsuch that when mounted upon the base substrate the at least one adhesive mass will co-operate with the package substrate and the base substrate to adhere the package substrate and the base substrate to each other.