Method for forming plastic packages, in particular thin packages, for

Abstract

The invention relates to a method for forming a plastic package for an integrated electronic semiconductor device to be encapsulated within a plastic body, being of the type which comprises the step of molding said plastic body so as to fully enclose a semiconductor element, on which an integrated electronic circuit has been formed and which is placed onto a metal leadframe connected electrically to said integrated electronic circuit and carrying a plurality of terminal leads for external electric connection. To compensate the outward bends uncontrollably undergone by the plastic body due to thermal stresses during the molding step, a mold is used which has a cavity delimited by perimeter walls which define a concave-shaped volume. Preferably, at least one of the large walls, a bottom wall and a top wall, has a curvature inwardly of said mold cavity. The curvature values are predetermined to compensate any outward curvature undergone by corresponding surfaces of said plastic body during the molding step. The plastic package thus obtained exhibits, at the end of the molding step, a body having a diversified thickness which is at a maximum near the edges and at a minimum in the central portion; the difference between these thicknesses is proportional to the amount of the relative deformation undergone by the central regions of the body surfaces with respect to the regions near the edges. The plastic body is within ideal overall dimensions.