| AVS 63rd International Symposium & Exhibition | |
| Applied Surface Science | Wednesday Sessions |
| Session AS-WeA |
| Session: | Multiple Technique Approaches for Real-World Industrial Problem Solving |
| Presenter: | Jeffrey Fenton, Medtronic plc |
| Authors: | J. Fenton, Medtronic plc L. Nygren, Medtronic plc B. Tischendorf, Medtronic plc R. Jahnke, Medtronic plc J. Heffelfinger, Medtronic plc |
| Correspondent: | Click to Email |
Since the first pacemaker implant in 1958, engineering and medical advances have greatly improved device capabilities and patient outcomes. Advances in materials chemistry have increased the need for deep understanding of process-material interactions and their role in device or component longevity. This presentation will focus on the utilization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) on processes related to two device components, feedthroughs and printed wire boards, as a means to improve processing conditions, expand processing boundaries, and understand failure modes.
In pacemakers or like devices, feedthroughs are evaluated using various electrical tests to determine the insulation resistance which is typically in the Megaohm or Gigaohm range. XPS and SEM analysis will be shown to aid in the determination of yield loss root cause by identifying sources of foreign materials. For example, fibers from clothing may deposit onto the insulator and graphitize during high temperature processes. The graphitized materials may then provide a pathway for conductivity during electrical testing. Compositional and morphological identification with SEM allows for root cause identification and elimination of those yield losses.
Laser soldering, which is relatively new to the industry, is utilized in new Medtronic products. During the laser soldering process localized heat results in a different wetting dynamic from the conventional furnace reflow. The laser soldering process may be used after preceding thermal exposure in the upstream processes resulting in changes to the surface condition of the soldering pads. The surface chemistry may change during thermal exposure which may cause reduced wettability and create one of the biggest challenges during the process development to overcome. XPS, SEM and XRF (x-ray fluorescence) methods provide key insight on the inter-diffusion between the metallization layers on the PBW and migration to the surface species that can limit pad solderability. The main outcome of the analysis was establishing design rules for the PWB plating, including metallization materials and layer thickness in multilayer metallization.