ump ing ▁capabilities ▁exceed ing ▁ 1 5 0 ▁W / cm 2 ; ▁and ▁when ▁subject ed ▁to ▁heat , ▁have ▁demonstrated ▁the ▁cap ability ▁to ▁generate ▁up ▁to ▁ 1 0   m W ▁of ▁power ▁per ▁b ump . ▁ ▁Th erm al ▁co pper ▁pill ar ▁b ump ▁structure ▁Figure ▁ 3 ▁shows ▁an ▁SE M ▁cross - section ▁of ▁a ▁TE ▁leg . ▁ ▁Here ▁it ▁is ▁demonstrated ▁that ▁the ▁thermal ▁b ump ▁is ▁struct ur ally ▁identical ▁to ▁a ▁CP B ▁with ▁an ▁extra ▁layer , ▁the ▁TE ▁layer , ▁incorpor ated ▁into ▁the ▁stack - up . ▁The ▁addition ▁of ▁the ▁TE ▁layer ▁transform s ▁a ▁standard ▁co pper ▁pill ar ▁b ump ▁into ▁a ▁thermal ▁b ump . ▁ ▁This ▁element , ▁when ▁properly ▁configured ▁elect r ically ▁and ▁therm ally , ▁provides ▁active ▁therm oe lect ric ▁heat ▁transfer ▁from ▁one ▁side ▁of ▁the ▁b ump ▁to ▁the ▁other ▁side . ▁ ▁The ▁direction ▁of ▁heat ▁transfer ▁is ▁dict ated ▁by ▁the ▁do ping ▁type ▁of ▁the ▁therm oe lect ric ▁material ▁( e ither ▁a ▁P - type ▁or ▁N - type ▁sem icon duct or ) ▁and ▁the ▁direction ▁of ▁electric ▁current ▁passing ▁through ▁the ▁material . ▁This ▁type ▁of ▁therm oe lect ric ▁heat ▁transfer ▁is ▁known ▁as ▁the ▁P elt ier ▁effect . ▁Con vers ely , ▁if ▁heat ▁is ▁allowed ▁to ▁pass ▁from ▁one ▁side ▁of ▁the ▁therm oe lect ric ▁material ▁to ▁the ▁other , ▁a ▁current ▁will