InkJet Printing As Alternative Approach To Conventional Spin-on Material Coatings

Polymer dielectrics have been in use for various layers in IC packages starting from substrates up to Epoxy Molding Compounds. There is a variety of various polymer chemistry approaches applied, mainly polyimides, polybenzoxazoles, epoxy resins and benzocyclobutene. Processing from solution in combination with photolithography has been the main technique to make small features e.g. for Re-Distribution Layer (RDL) or Stress Buffer (SB) applications. That method has been perfected over the years and delivers the required patterns and yield on the production. It is considered as standard process by default for enabling the assembly of flip-chip packages. However, spin-coating followed by photolithography is known to be rather wasteful, with only 10-20% of material staying on the substrate after patterning - all because it is subtractive method. In this paper we present InkJet printing as an alternative additive method approach for selected applications, where features' resolution is pushing beyond 20-50um line/spacing.