▁highly ▁conduct ive ▁path ways ▁for ▁collect ing ▁heat ▁from ▁the ▁underlying ▁circuit ▁and ▁fun nel ing ▁that ▁heat ▁to ▁the ▁thermal ▁b ump . ▁ ▁The ▁metal ▁traces ▁shown ▁in ▁the ▁figure ▁for ▁conduct ing ▁electric ▁current ▁into ▁the ▁thermal ▁b ump ▁may ▁or ▁may ▁not ▁be ▁directly ▁connected ▁to ▁the ▁circuit ry ▁of ▁the ▁chip . ▁ ▁In ▁the ▁case ▁where ▁there ▁are ▁elect rical ▁connections ▁to ▁the ▁chip ▁circuit ry , ▁on - board ▁temperature ▁sens ors ▁and ▁driver ▁circuit ry ▁can ▁be ▁used ▁to ▁control ▁the ▁thermal ▁b ump ▁in ▁a ▁closed ▁loop ▁fashion ▁to ▁maintain ▁optimal ▁performance . ▁ ▁Second , ▁the ▁heat ▁that ▁is ▁p ump ed ▁by ▁the ▁thermal ▁b ump ▁and ▁the ▁additional ▁heat ▁created ▁by ▁the ▁thermal ▁b ump ▁in ▁the ▁course ▁of ▁p ump ing ▁that ▁heat ▁will ▁need ▁to ▁be ▁rejected ▁into ▁the ▁substr ate ▁or ▁board . ▁ ▁Since ▁the ▁performance ▁of ▁the ▁thermal ▁b ump ▁can ▁be ▁improved ▁by ▁providing ▁a ▁good ▁thermal ▁path ▁for ▁the ▁rejected ▁heat , ▁it ▁is ▁benef icial ▁to ▁provide ▁high ▁therm ally ▁conduct ive ▁path ways ▁on ▁the ▁back side ▁of ▁the ▁thermal ▁b ump . ▁ ▁The ▁substr ate ▁could ▁be ▁a ▁highly ▁conduct ive ▁cer am ic ▁substr ate ▁like ▁Al N ▁or ▁a ▁metal ▁( e . g ., ▁Cu , ▁Cu W , ▁Cu Mo , ▁etc .) ▁with ▁a ▁die lect ric . ▁In ▁this ▁case , ▁the ▁high ▁thermal ▁conduct ance ▁of ▁the ▁substr ate ▁will ▁act ▁as