Indium Blog

Chip on Flex

  • Flux
  • Indium Corporation
  • No Clean Flux

  • Flexible circuits help us fit electronics in confined spaces better than conventional FR4 type PCBs.  Along with the flexibility comes a challenge of reliably mounting chips on a flexible substrate.  Generally, chips on flex use underfill to protect the component and interconnections, and add a level of reliability to the process.  If a capillary underfill is in order, than the proper flux needs to be selected.  I have 2 recommendations:



    • NC-510 for no clean applications, it has an ultra-low post reflow residue level.  This will help the underfill flow faster, and more completely.


    • WS3622 for water soluble applications.  This flux cleans easily, so the easily permeated flexible substrate does not need to spend excess time in contact with water.


    Authored by previous Indium Application Manager Jim Hisert