fig1 illustrates a top - down plan view of the super bga package 30 of the preferred embodiment of the present invention showing the slots 28 formed within the heat spreader / substrate 26 centered over the semiconductor chip / die 10 represented by area 10 ′. slots 28 do not completely pierce heat spreader 26 so as to prevent deleterious effects of moisture , for example , on the underlying super ball grid array ( sbga ) chip 12 . semiconductor chip / die 10 is preferably comprised of silicon ( si ) or germanium ( ge ) and is preferably silicon as will be used for purposes of illustration hereafter . it is noted that while an sbga chip is illustrated in the figs ., the concepts of the present invention may also be applied to traditional hsbga and hsfcbga chips . heat spreader 26 is preferably comprised of copper ( cu ), aluminum ( al ), chromium ( cr ) plated on cu or al or nickel ( ni ) plated on cu or al and is more preferably ni plated on cu . the coefficient of thermal expansion ( cte ) of the heat spreader 26 is preferably from about 10 to 25 depending upon the materials and is more preferably about 17 for copper ( cu ). slots 28 are arranged in a pattern around , but not over , silicon semiconductor chip / die 10 ( area 10 ′ in fig1 ). the number or density of slots 28 are determined by a simulation of finite analysis that balances stress - reduction , heat - release and mechanically - robust performance and depends upon the die size , produced heat and environmental conditions . the patterns for slots 28 may be that shown in fig1 , i . e . parallel / perpendicular rows , or , for further examples , those shown in fig3 a to 3 g such as , for example , circular , radiated , rectangular , square , concentric circular , concentric square , concentric octagonal etc . individual slots 28 may be rectangular as shown in fig1 and 2 , square , triangular , circular , polygonal , etc . and are more preferably rectangular . when in the pattern specifically shown in fig1 , slots 28 within a row facing area 10 ′ are preferably spaced apart from each other by from about 0 . 5 to 2 . 5 mm and more preferably from about 0 . 7 to 1 . 5 mm and the rows are spaced apart from each other by from about 1 . 0 to 5 . 0 mm and more preferably from about 1 . 5 to 2 . 5 mm . fig2 illustrates a cross - sectional view of fig1 along line 2 - 2 showing heat spreader 26 mounted over super ball grid array ( sbga ) chip 12 with slots 28 outboard of the silicon semiconductor chip / die 10 . the remaining thickness of heat spreader 26 at slots 28 as at 29 is preferably from about 15 to 75 % of the thickness of the heat spreader 26 and more preferably from about 25 to 50 % of the thickness of the heat spreader 26 . thus , slots 28 penetrate the heat spreader 26 by preferably from about 85 to 25 % and more preferably from about 75 to 50 %. the slots 28 may be set on the die area . the super ball grid array ( sbga ) chip 12 includes silicon semiconductor chip 10 mounted onto a substrate 14 and is electrically connected to substrate 14 by , for example , lead wire structures 16 . substrate 14 has an upper layer 15 and a lower layer 17 . upper layer 15 is preferably from about 0 . 3 to 1 . 75 mm thick and is more preferably from about 1 . 0 to 1 . 5 mm thick and is preferably comprised of a copper ( cu ) ring ( for 2 laminated structure which is most used ) or polyimide dielectric , polymer , cu ( metal trace ), resin , etc . and more preferably a copper ring ( for 2 laminated structure ). lower layer 17 is preferably from about 0 . 2 to 1 . 5 mm thick and is more preferably from about 0 . 3 to 1 . 0 mm thick and is preferably comprised of polyimide dielectric , polymer , cu ( metal trace ), resin , solder resist , etc . substrate 14 includes balls 18 mounted on its surface opposite the heat spreader 26 . balls 18 are preferably comprised of 63sn37pb ( 63 % sn + 37 % pb — likely to be forbidden due to environmental protection ), 96 . 5sn3 . 5ag ( 96 . 5 % sn + 3 . 5 % ag — lead - free and expected to be used in the future due to environmental protection ), 95 . 5sn3 . 8ag0 . 7cu ( 95 . 5 % sn + 3 . 8 % ag + 0 . 7 % cu — lead - free ) or 96 . 2sn2 . 5ag0 . 8cu0 . 5sb ( 96 . 2 % sn + 2 . 5 % ag + 0 . 8 % cu + 0 . 5 % sb — lead - free ) and are more preferably 63sn37pb for the present and 96 . 5sn3 . 5ag if 63sn37pb is banned . encapsulate 40 encapsulates the otherwise exposed silicon semiconductor chip / die 10 and lead wire structures 16 and protects it from moisture and chemical and physical insult . encapsulate 40 is preferably comprised of epoxy resin , filler , curing agent , etc . semiconductor chip / die 10 generally has a coefficient of thermal expansion ( cte ) of preferably from about 2 . 5 to 3 . 5 and more preferably about 2 . 8 when comprised of silicon and from about 5 . 5 to 6 . 5 and more preferably about 6 . 1 when comprised of germanium and heat spreader 26 generally has a cte of preferably from about 10 to 25 and more preferably about 17 for copper ( cu ) depending upon the materials . this juxtaposition of materials having such dissimilar ctes is mitigated by the use of slots 28 within heat spreader 26 which serve to release accumulated thermal expansion stress and thus reduce the impact upon the underlying ( silicon ) semiconductor chip / die 10 and the sbga chip 12 . the three - dimensional nature of slots 28 improves the thermal effectiveness of the heat spreader 26 with lower stress impact on lk semiconductor chips / dies 10 . the instant invention applies slots 28 on the metal substrate / heat spreader 26 to reduce expansion stress impact of the metal substrate / heat spreader 26 on the low - k die / semiconductor chip 10 . as noted above , varying slot types and slot patterns / distributions are acceptable . this concept may be applied not only to sbga &# 39 ; s but also with other packages with heat spreaders such as hsfcbga &# 39 ; s and hsbga &# 39 ; s which are hard to assemble lk dies . the advantages of one or more embodiments of the present invention include : 1 . realize sbga package types on lk dies ; 2 . enhance heat - releasing performance ; 3 . no extra assembly process or tools are needed ; and 4 . the same slot concept can be applied on the heat spreader of other packages . while particular embodiments of the present invention have been illustrated and described , it is not intended to limit the invention , except as defined by the following claims .