Image Component

Meeting the horizontal electroless copper plating challenge

Feng Liu
Dow Electronic Solutions R&D scientist, Interconnect Technologies Liu’s research interests are ionic and nanoparticle catalyst, electroless and electrolytic copper metallization, and electrolytic nickel metallization.

Electronic devices have become an indispensable part of people’s daily life in every corner of the globe. Performance of such devices is evolving at a tremendous rate, driven by both semiconductor technology and software advances. In recent years, along with the reduction in size and increased performance of electronic devices, the packaging density of electronic circuits has become higher and subsequently required to be defect-free after electroless plating.

The most commonly used method to catalyze or activate laminated non-conductive dielectric substrate regions, prior to electroless plating, is to treat the board with an aqueous palladium-tin colloid in an acidic medium. As a result of greater demands on reliability and the increased complexity of these high-density-interconnect (HDI) and integrated circuit (IC) package substrate boards, new innovations are necessary to meet these metallization requirements. Novel catalysts expand our portfolio beyond the current Pd/Sn colloidal catalyst technologies, which have been used commercially as activators for electroless metal deposition for decades, and enable our customers to meet the ever increasing performance demands. In this post, we introduce Circuposit™ 6530 Catalyst developed specifically for horizontal electroless Cu plating.

Catalytic systems based on ionic solutions have several important advantages over the colloidal catalysts currently employed. The ionic catalyst complexes have intrinsically superior stability to oxidizing environments, such as the high agitation typically found in horizontal conveyorized equipment, due to the absence of extraneous metal ions, particularly Sn2+. Additionally, the ionic catalyst complexes enable penetration and surface activation of even the deepest substrate recesses while maintaining wide operating parameters with ease of process control. Finally, these catalysts provide the reduced residual conductivity necessary for fine line technology typically found in these complex designs.

For these high density interconnects, horizontal processing is the preferred technology given that a conveyorized system can more readily handle thin core processing. Additionally, the improved solution flow can easily meet the uniformity requirements of these complex microstructures on both sides of the panels through consistent catalyst application and chemical treatment. High-end structures also require multiple metallization cycles, wherein productivity is an issue, giving horizontal processing the advantage.

In response to customer needs for a drop-in solution for HDI and IC package substrate boards plated in horizontal conveyorized equipment, Dow Electronic Solutions developed the Circuposit™ 6530 Catalyst, an ionic palladium catalyst designed specifically for use in this application. The ionic palladium catalyst demonstrates stable bath life and reliable performance over a wide process window. It provides high reliability performance by ensuring uniform coverage throughout features while maintaining high Cu-Cu joint reliability to withstand the physical, thermal, and chemical stresses of additional processing as well as throughout the final device life.

Want to learn more? Read the paper titled “Circuposit™ 6530 Catalyst Process for Electroless Copper Metallization,” which details the reliability performance and horizontal electroless Cu plating processes using this formulation, and has been presented on Oct. 22 at the 2015 IMPACT Forum.

Topic Tags