Laser Cleaning Polyimide Film

Polyimide film is a kind of dielectric insulating material needed to encapsulate the internal multilayer connection structure of high-density electronic components. In the process of packaging, it is necessary to drill holes in the polyimide film, manufacture surface micro structure circuit patterns and arrange high-density wiring (these processes can be completed by using all solid state UV lasers with high repetition rate). In these processes, polyimide is often polluted by Ti, Cr, W, Ni or Pb, while traditional chemical methods cannot achieve thorough cleaning. Due to its high photon energy, UV laser can break the molecular chain of polyimide and clean up the pollution by peeling off the film, which has become an effective method for packaging high-density electronic components.

All solid state UV laser and excimer laser peeling polyimide technology have been widely used in the whole process of electronic component packaging. For example, chromium contamination on a 15 um thick polyimide film prepared with mutually insulating gold structures was cleaned with 193 nm excimer laser, and peeling started at an energy density of 22 MJ / cm2. When the energy density was increased, the peeling rate increased slowly, and became saturated after 1 J / cm2. However, for 248nm KrF excimer laser cleaning, peeling starts at an energy density of about 30MJ / cm2, and the peeling rate rapidly accelerates with the increase of energy density. At 1J / cm2, the peeling thickness per pulse reaches 0.36um. This may be due to the thermal effect in addition to the photoinduced effect of 248 nm stripping.