Advancements in Packaging Technology Driven By Global Market Return
This article is based on an original publication by Henkel.
With an emphasis on new technologies, the IC packaging and design industry continues to experience accelerated growth while materials suppliers invest their resources into delivering market-ready materials. Recent innovations include Wafer Backside Coating Technology (WBC), compression mold materials, electrically conductive adhesives for assembly of photovoltaic modules, thermo-compression flip-chip and epoxy flux technology for improved reliability solder interconnections.
Wafer Backside Coating Technology
While technicians have used traditional silver-filled die attach adhesives to bond ICs to leadframes and laminate substrates for decades, the WBC technology addresses a number of issues in the conventional process. Traditionally, paste is dispensed onto the leadframe, and the chip is placed into the paste. The pad must be significantly larger than the chip to allow for the flow of the paste and the formation of a fillet around the die edge. And, the die must be thin enough to prevent the paste from flowing onto the top of the chip. During a WBC application, a b-stage paste is coated on the backside of a wafer prior to dicing. The development of wafer backside coating materials has facilitated thinner bondlines, lower total package cost and improved manufacturing throughput.
Compression Mold Materials
Compression molding is a viable option to transfer molding in a number of applications, including eWLB, MCP and SiP. Compression molding is gaining popularity as it allows for a larger area to be molded at once, which improves manufacturing throughput and minimizes waste. It also eliminates a number of materials and/or process steps used in advanced packages.
Electrically Conductive Adhesives for Assembly of Photovoltaic Modules
Applications relying on temperature sensitive substrates, such as organic solar cells, require low temperature interconnection processes. While electrically conductive adhesives have been used for years as an alternative to traditional solders, the major limitation, until recently, has been their instability on non-noble electronic termination metals like coper and tin. The unstable contact resistance is due to electrochemical corrosion of the metals under elevated temperature and humidity. As a result, a new class of conductive adhesives was developed. Products employing the corrosion inhibitors have been successfully incorporated into thin-film solar substrate applications.
A recently developed non-conductive paste (NCP) has facilitated faster bonding time and good reliability when used during thermo-compression flip-chip device assembly in very fine-pitch applications, including copper pillar and gold-stud, flip-chip interconnects. While flip-chip devices typically use solder reflow to form the electrical interconnect, very fine-pitch devices cannot employ conventional solder reflow due to bridging. Devices assembled via the improved, thermo-compression flip-chip process continue to pass performance tests.
Epoxy Flux Technology for Improved Reliability Solder Interconnections
Until the advent of epoxy flux, underfill materials were failing to meet the industry's changing demands toward higher density, flexible and miniaturized devices and component configurations. Now, this breakthrough underfill material offers process efficiency by way of solder joint formation. It also offers device protection by encapsulating individual bumps. Epoxy fluxes provide an in-line alternative to other underfill methods because they are cured during the reflow process. Depending on the process, the need for a dedicated dispensing system and the time required to dispense and cure may be eliminated with epoxy flux. Additionally, these new materials may be screen printed, dipped, jetted or dispensed as required depending on the application and process. For fine-pitch assembly, the technology improves manufacturing rates and reliability. Because epoxy flux serves as both flux and underfill, its application range is broad for packaging and board assembly environments.
Innovative technologies in IC package design and manufacture, including WBC, compression mold materials, electrically conductive adhesives for assembly of photovoltaic modules, thermo-compression flip-chip and epoxy flux technology for improved reliability solder interconnections, continue to accelerate the growth of the IC packaging market.