▁chip ▁level ▁by ▁using ▁more ▁thermal ▁b umps ▁in ▁the ▁overall ▁design . ▁ ▁A ▁brief ▁history ▁of ▁sol der ▁and ▁f lip ▁chip / ch ip ▁scale ▁pack aging ▁S older ▁b ump ing ▁technology ▁( the ▁process ▁of ▁joining ▁a ▁chip ▁to ▁a ▁substr ate ▁without ▁short ing ▁using ▁sol der ) ▁was ▁first ▁conce ived ▁and ▁implemented ▁by ▁IBM ▁in ▁the ▁early ▁ 1 9 6 0 s . ▁ ▁Three ▁versions ▁of ▁this ▁type ▁of ▁sol der ▁joining ▁were ▁developed . ▁ ▁The ▁first ▁was ▁to ▁embed ▁co pper ▁balls ▁in ▁the ▁sol der ▁b umps ▁to ▁provide ▁a ▁positive ▁stand - off . ▁ ▁The ▁second ▁solution , ▁developed ▁by ▁Del co ▁Electron ics ▁( General ▁Mot ors ) ▁in ▁the ▁late ▁ 1 9 6 0 s , ▁was ▁similar ▁to ▁embedding ▁co pper ▁balls ▁except ▁that ▁the ▁design ▁employed ▁a ▁rig id ▁silver ▁b ump . ▁The ▁b ump ▁provided ▁a ▁positive ▁stand - off ▁and ▁was ▁attached ▁to ▁the ▁substr ate ▁by ▁means ▁of ▁sol der ▁that ▁was ▁screen - print ed ▁onto ▁the ▁substr ate . ▁The ▁third ▁solution ▁was ▁to ▁use ▁a ▁screen ed ▁glass ▁dam ▁near ▁the ▁electro de ▁tips ▁to ▁act ▁as ▁a ▁‘ ‘ stop - off ’ ’ ▁to ▁prevent ▁the ▁ball ▁sol der ▁from ▁flow ing ▁down ▁the ▁electro de . ▁By ▁then ▁the ▁Ball ▁Lim iting ▁Met all ur gy ▁( BL M ) ▁with ▁a ▁high - le ad ▁( P b ) ▁sol der ▁system