Optical FPC Assembly

This project evaluates the various manufacturing options for attaching very fine pitch flexible printed circuits typically used to connect optical transceiver modules to PWBs. The project will explore several different attachment techniques assessing their suitability for high volume high yielding assembly applications.

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Idea Information



Optical transceivers are increasingly being adopted for use in data products to address the demand for ever increasing bandwidth and speed. The transceiver components are typically connected to PWB modules via flexible printed circuits  (FPCs). The FPCs using local heating techniques (hot thermode bar being the most prevalent at this time). 

The dominant trend for miniaturization of electronic products at all levels dictates that optical module designs and the space available to attach them to other electronic circuitry continues to shrink. This has a direct impact on the pitch of the connections on the FPCs. Moreover, limited attachment space is driving the need for multiple rows of connection pads and in many cases irregular shaped (e.g. U shaped) layouts are used.



The typical minimum connection pitch for FPCs used in optical component attachment is currently around 0.8mm. However future demands indicate that this pitch will need to be significantly reduced to 0.4mm for mainstream applications and possibly down to 0.2mm for certain proroduct requirments. At these pitches currently established connector attachment techniques are being severely challanged with a negative impact on yields and quality. In order to achieve acceptable high volume assembly  process optimization and potentially new attachment technques are needed.

Definition Information

Goals / Benefits: 


The goal of this project is to evaluate and optimize a process solution for attaching optical component flexible printed circuits (FPC) with 0.3mm/0.4mm pitch design.


  • Explore various assembly process options to improve the yield for finer pitch FPC device
  • Establish a simple, acceptable test method to evaluate the reliability of different FPC designs,  including  different  FPC materials, solder pad pitch,  geometry structure, assembly process.


High level objectives: 
  1. Design a test vehicle that can be used for both process characterization and reliability testing.
  2. Explore and evaluate soldering and assembly process methods (hot bar soldering, laser soldering, anisotropic conductive film (ACF), and microwave) targeting a 99% assembly yield target.
  3. Define test processes and methodologies to evaluate the reliability of these FPC designs.
  4. Publish guidelines that can potentially be adopted in a general qualification standard for FPC+PCB assemblies

The project will be run on a phased approach:

  • Phase 1 Hot Bar and ACF* – Current Phase
  • Phase 2 Laser soldering
  • Phase 3 Microwave Assembly
  • Phase 4 Other Method?
(* ACF – Anisotropic conductive film)




Key Participants: 
TTM Technologies