October 27, 2017

Smaller interconnects are required for many of the new applications and dense components on the market. High Density Interconnect, or HDI, is the process of leveraging manufacturing capabilities and materials to create very small interconnect solutions. HDI Flexible Printed Circuits are more dense than conventional Flexible Printed Circuits (FPC). HDI technology increases density by miniaturization of holes, pads, and conductors.

PFC is committed to HDI and has invested R&D dollars and resources to improving and providing HDI solutions to the market. HDI FPC requires the flex circuit vendor to design manufacture and assemble. This is the charter of PFC.

Benefits of HDI

  • Higher density packaging
  • Improved signal integrity because of reduced track length
  • Improved thermal performance and reliability
  • Advanced component packaging – provides the possibility to have a via hole connect directly in the SMD or BGA pad
  • More design options and flexibility
  • Improved possibility to maximization of ground connections

HDI Applications

  • Digital handheld devices
  • High-end Datacom/telecom market for high-speed applications
  • Semiconductor test equipment
  • Wearable medical devices

High-Density Interconnect (PFC standard capability)

  • PFC finer lines and spaces (≤50 um = 2mil), smaller vias (<100um = 4mil) and capture pads (<400um = 16mil)
  • Microvia formed by laser a blind hole with a diameter (≤100 um = 4mil) having a pad diameter (≤400 um = 16mil)
  • Mechanical drilling capability a diameter (≤150 um = 6mil) having a pad diameter (≤400 um = 16mil)
  • PFC leading-edge capability for laser drilling (50um = 2mil) having a pad diameter (≤380 um = 15mil)
  • Aspect ratio on blind via should be under 1:1

HDI Materials

Very thin copper materials are essential to creating high density solutions. 12 micron copper is what is used in many cases to create HDI solutions. PFC is now evaluating/qualifying even thinner materials.

  • 12um RA copper is already a standard product – we did a small project with 9um RA copper but still considered as R&D
  • Thinner coverlays 12.5 um PI with 12.5um Adhesive
  • Low loss laminates as well as low dielectric constants (TK, Taconic & *LCP) *under evaluation
  • Higher heat resistance is needed for lead-free assembly processes

HDI Assembly

Many industry flex circuit gurus discuss HDI based on the density of the package – the circuit itself. However, in addition to the package, an HDI flex requires HDI assembly.

PFC has been assembling flex in-house for more than ten years. Approximately 90% of PFC’s customers now receive an assembled flex circuit.

For HDI assembly, PFC has been placing 1005 components for more than 18 months and has the ability to place 12 mil pitch BGAs.

Contact PFC for further information on HDI.