Abstract
We demonstrated the applicability of dry film photoresists (DFR) in photolithography process for fine pitch bumping on the polytetrafluoroethylene (PTFE/Teflon/spl reg/) printed circuit board (PCB). The copper lines were formed with 100/spl mu/m width and 18/spl mu/m thickness on the PTFE test board, and varying the gaps between two copper lines in a range of 100-200/spl mu/m. The DFRs of 15/spl mu/m thickness were laminated by hot roll laminator, by varying laminating temperature from 100/spl deg/C to 150/spl deg/C and laminating speed. We found the optimum process of DFR lamination on PTFE PCB and accomplished the formation of indium solder bumps. The optimum lamination condition was temperature of 150/spl deg/C and speed of about 0.63cm/s. And the smallest size of indium solder bump was diameter of 50/spl mu/m with pitch of 100/spl mu/m.
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