ps ), ▁las er ▁di odes , ▁and ▁sem icon duct or ▁optical ▁ampl ifiers ▁( SO A ). ▁Un like ▁conventional ▁sol der ▁b umps ▁that ▁provide ▁an ▁elect rical ▁path ▁and ▁a ▁mechanical ▁connection ▁to ▁the ▁package , ▁thermal ▁b umps ▁act ▁as ▁solid - state ▁heat ▁p umps ▁and ▁add ▁thermal ▁management ▁functionality ▁locally ▁on ▁the ▁surface ▁of ▁a ▁chip ▁or ▁to ▁another ▁elect rical ▁component . ▁The ▁diameter ▁of ▁a ▁thermal ▁b ump ▁is ▁ 2 3 8 ▁ μ m ▁and ▁ 6 0 ▁ μ m ▁high . ▁ ▁The ▁thermal ▁b ump ▁uses ▁the ▁therm oe lect ric ▁effect , ▁which ▁is ▁the ▁direct ▁conversion ▁of ▁temperature ▁differences ▁to ▁electric ▁voltage ▁and ▁vice ▁vers a . ▁Sim ply ▁put , ▁a ▁therm oe lect ric ▁device ▁creates ▁a ▁voltage ▁when ▁there ▁is ▁a ▁different ▁temperature ▁on ▁each ▁side , ▁or ▁when ▁a ▁voltage ▁is ▁applied ▁to ▁it , ▁it ▁creates ▁a ▁temperature ▁difference . ▁This ▁effect ▁can ▁be ▁used ▁to ▁generate ▁electric ity , ▁to ▁measure ▁temperature , ▁to ▁cool ▁objects , ▁or ▁to ▁heat ▁them . ▁ ▁For ▁each ▁b ump , ▁therm oe lect ric ▁cool ing ▁( TE C ) ▁occurs ▁when ▁a ▁current ▁is ▁passed ▁through ▁the ▁b ump . ▁The ▁thermal ▁b ump ▁pull s ▁heat ▁from ▁one ▁side ▁of ▁the ▁device ▁and ▁trans fers ▁it ▁to ▁the ▁other ▁as ▁current ▁is ▁passed ▁through ▁the ▁material . ▁This ▁is ▁known ▁as ▁the ▁P elt ier ▁effect . ▁The ▁direction ▁of ▁he