Nina Dambrowsky

Filling through holes and blind microvias with copper using reverse pulse plating and insoluble anodes

Purpose – The purpose of this paper is to present a summary of development work made in technical centres and on the subsequent customer qualification of copper filled through holes and blind microvias.Design/methodology/approach – Various copper deposition parameters were investigated in a small‐scale production line which was then extended to full‐scale production qualification in a horizontal conveyorised system. Samples of substrates with copper filled through holes were qualified at end‐user facilities.Findings – The copper plating process may be used to replace an existing production process for printed circuit boards. The proposed system can give a more reliable result in terms of filling and technical capability for the produced substrate. Overall production cost savings are possible.Research limitations/implications – The technology is based on a copper plating electrolyte using a redox pair for copper replenishment. The results achieved depend on use of this system and on production equipment wh...

Via filling: Challenges for the plating process for conveyorised production

Copper filling of laser drilled blind micro vias (BMVs) is now the standard production method for high density interconnects. Copper filled BMVs are used as solder bump sites for IC packaging where the filling process enables the required interconnect density and provides the surface to ensure reliable solder attachment. For “smart phone” production use of multiple lamination and typically 10 layers of stacked copper BMV filling is now the preferred technology, this is also known as the “any layer” filling process. Advances in filling processes are required to maintain the development in circuit miniaturization together with the reduction in overall processing costs and to meet the demand for ever more filled BMVs on each plated layer. The required filling processes must provide void or inclusion free filling, a minimum of surface plated copper along with the capability to allow stacked filled structures. This paper describes the function and principles behind BMV filling processes together with methods for non destructive testing of the filled structures. Production processes for BMV filling in vertical and horizontal production equipment with both soluble and insoluble anodes are presented together with a discussion of the plating parameters currently used in volume production. A comparison in filling performance of DC plating with that achieved in reverse pulse plating is also made. Current production systems for BMV filling are usually conveyorized to meet the required production targets in terms of volume and uniformity. High relative electrolyte loading in such systems requires uniform processing parameters and tight control. Examples of fully automatic analysis and control systems for copper plating additives and inorganic components are shown.