Abstracts: Advanced Packaging and Its Impact on mmWave Applications
The Future of Heterogeneous Integration: Challenges and Opportunities
Emerging electronic systems require dense integration of many chiplets in either 2D or 3D form. The metrics for these systems will be dictated by power, performance, form factor, cost, and reliability. The complexity of these systems is expected to be large given the integration of sensing, wireless, computing, and other functionality on a single packaging platform that combines electronics and photonics together. Such systems pose immense integration challenges but also provide opportunities for innovation on several fronts that include architecture, design, thermal, materials, embedded intelligence, and many more. This presentation will provide a discussion of the state of the art and opportunities for the future.
Dr. Madhavan Swaminathan, The Pennsylvania State University
Devices utilizing copper pillar technology have more interconnects per surface area resulting in tighter pitch and lower standoff heights. As standoff height reduces, flux residues have less area to outgas during reflow. For that reason, there is a critical need to investigate the conditions that would be required to successfully remove flux residues to ensure the functionality and reliability of the final product.
Flux residues can affect reliability, especially with respect to underfill, in two ways. First, if flux residue is present on the solder bump, substrate or die, it can significantly reduce interfacial adhesion between the underfill and the surfaces. Once the underfilled device is stressed by thermal shock, humidity or other factors, the underfill delaminates from the surface, and a gap can be detected using acoustic microscopy. Second, fluxes can affect reliability by physically impeding the flow of underfill material. Flux residue buildup in the gap between bumps or between the die and the substrate can narrow the gap to a point where the underfill cannot flow or the edges flow faster, encapsulating air and creating a void. To ensure a void-free underfill, homogenous wetting of the underfill must occur on all surfaces. If wetting is not homogeneous, voids in the uncured underfill may translate into reliability problems later.
This presentation reports on a study that used straight DI-water and novel low-concentration alkaline cleaning agent on copper pillar bumped flip chips. The challenge was to effectively clean flux residues underneath these components. The outcome of this study could provide a benchmark for conducting further studies involving bump pitch lower than 15 μm and denser packages including 2.5Ds and 3Ds. The cleaning assessment methodologies employed analytical/functional testing including FTIR, ion chromatography, SEM/EDX, thermal cycling (TC) test, underfill test, high temp storage life (HTSL) test and moisture sensitivity level 3 (MSL-3) testing.
NOTE: this presentation is based on a paper presented at IPC APEX 2022, co-authored by Ravi Parthasarathy and Umut Tosun, ZESTRON Corporation (Manassas, VA USA).
Novel Magnetically Aligned Anisotropic Conductive Epoxy for Electronics Interconnection and Semiconductor Packaging
SunRay Scientific will present a novel, magnetically aligned anisotropic conductive epoxy, ZTACH® ACE, which provides unique electronic interconnects (ICs) and structural integrity with lower curing temperatures, no pressure, in less space and lower weight to achieve substantial improvements relative to traditional IC methodologies.
Madhu Stemmermann, SunRay Scientific
ZTACH® ACE is a multifunctional interconnect material including an electromagnetic processing technology, that has been successfully developed as an alternative to traditional IC methodologies such as low temperature solder, conductive epoxy, Anisotropic Conductive Adhesive (ACA), Anisotropic Conductive Film (ACF), indium bump bonding, and wire bonding. ZTACH® ACE consists of ferromagnetic particles randomly dispersed in an epoxy, aligned into z-axis conductive “columns” between the device and circuitry, during the cure process in the magnetic field of the ZMAG™ Pallet. Once cured, the ferromagnetic columns are locked into place creating a low-resistance, anisotropic connection with incredible bond strength and excellent electrical insolation between columns. Since the technology is lead-free and low energy, the integration of this material opens the possibility of “greener” electronics manufacturing and a reduced carbon footprint. ZTACH® ACE does not require solder bumps nor patterning, eliminating costly photolithography as well as enabling the potential to bond at the wafer level vs. single die level. The material’s high mechanical strength can eliminate the need for encapsulation in many applications. Uniquely, ZTACH® ACE integrates into Surface Mount Technology (SMT) processes for assembly, unlike the sequential assembly of components when using traditional anisotropic conductive adhesive and films.
ZTACH® ACE is a lightweight electrical interconnection for a variety of applications, such as flexible and stretchable LED lighting panels, first responders’ smart medical blankets, and flexible electronic performance devices. Beyond Flexible Electronic applications, further advancements have been made in functionalizing semiconductors for varied applications. ZTACH® ACE technology has shown over 2X smaller footprint needs than comparable wire-bonding, with thinner and higher performance than comparable flip-chip. SunRay Scientific is currently working on prototyping ZTACH® ACE as a scalable, IC solution, demonstrating functional high density ultrafine pitch capabilities. Successful advancement has been achieved from 250-micron pitch down to 60-micron pitch. Proven reliability of this z-axis interconnect includes high RF bandwidth performance (1-90 GHz), excellent radiation hardness (100 Mrad), excellent cryogenic cycling temperature performance, outstanding adhesion, shear strength, high vibration resistance, and shock tolerance. Significant reductions in the packaging time and cost can be achieved relative to standard materials and methods.