Rework on Flex Material

Author: Dan Lilie

Abstract: Flexible substrates are used in 3D connection and mechatronic concepts for reducing the number of connectors needed. They can stand high dynamic bending and are capable of high speed interconnections between different circuit layers. In portable applications, maximum miniaturization can be achieved by folding the PCB. Typical applications are found in medical devices (hearing aids, insulin pumps, neurostimulator implants), consumer electronics (mobile phones, portable computers, cameras, TFT displays) or automotive systems (sensor modules, engine control units). Chip (or Die) on Flex rework is essentially a material handling issue. Thermal profiles reflect the lower substrate thermal mass as compared to a PCB - typically shorter duration and lower air temperatures to reach liquidus. Support of the flex circuit necessitates alternate vacuum clamping systems and the use of conductive, rather than convective, lower heating.