High Density Chip-on-Board (HDCOB)

NCMS Project #: 160207

Problem: In 1998, U.S. Electronics Industry Roadmaps projected packaging requirements necessary to realize high-density circuit functions at the system level circuit card assembly using current and next generation chip packaging technologies. The roadmaps predicted a requirement for a paradigm shift in approach in both areas; that is, the development of redistribution layer printed circuit boards (PCB) and chip-size packages (CSP). Application of these technologies was demanding the assembly capability in both the commercial and defense industries.


  • Each industry participant developed manufacturing capabilities, performed reliability tests and were ready to use the higher-density technology much sooner than otherwise would have occurred.
  • Development of the rework process of particular interest to the DoD logistics community as it helps prepare them for the introduction of these high-density, mixed component packaging technologies.

Key process findings:

  • Adding solder paste to solder balls of replacement parts during parts rework or replacement provided increased solder joint reliability during environmental stress tests compared to reworked parts  where additional solder was not applied.
  • Selection of a surface finish for PCB solder pads can have a significant impact on solder joint reliability.
  • Rework processes were developed as a key need and capability for the industry as well as the DoD depot participant as they prepare for the introduction of this technology.
  • Reworkable underfills are not yet ready for use on high-value, high-reliability products. Materials suppliers are continuing development efforts in this area.

Solution/Approach: To develop and demonstrate production-ready assembly processes and materials for mixed-technology surface-mount components to cost effectively meet the requirements of large area, high-density commercial assemblies, as well as, the harsher environments imposed by military and space applications.

DOD Participation:

  • U.S. Army (Tobyhanna Army Depot)
  • U.S. Navy (NSWC Crane)

Industry Participation:

  • Raytheon Systems
  • Benchmark Electronics
  • Storage Technology Corporation
  • UTC/Hamilton Standard
  • NCMS


Final Report