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.