Compliant semiconductor chip package with fan-out leads and method of making same

A semiconductor chip assembly, comprising

• (a) an expander ring having inner side walls defining an opening;
• (b) a semiconductor chip having side surfaces defining the perimeter of the chip, said chip being disposed within said opening of said expander ring so that said side surfaces of said chip and said inner side walls of said expander ring define a gap therebetween, said gap having a width between said inner side walls and said side surfaces;
• (c) an encapsulant disposed in the gap;
• and
• (d) leads extending from said chip across said gap;
• wherein
• w≧((CTEexpander ring−CTEchip)Xc)/(CTEencapsulant(1 +2p));
• where w is the width of the gap;
• CTEexpander ring is the coefficient of thermal expansion of the expander ring;
• CTEchip is the coefficient of thermal expansion of the semiconductor chip;
• X, is the shortest distance between a point on the outer perimeter of the semiconductor chip and the center of the semiconductor chip;
• CTEencapsulant is the coefficient of thermal expansion of the encapsulant;
• and p is the Poisson ratio for the encapsulant.