Electro-Chemical Migration 2

In our previous project Electro-Chemical Migration we found that a No Clean Flux, which is designed to leave a benign residue, can result in crevice and pitting corrosion. We also discovered the flux activators can remain on the board due to excessive flux or entrapment (ie,: Selective solder fixtures, Wicking into soldermask and Non solder mask defined pads).  We already knew that harsh environments subjects devices to high humidity.  This all means that Ions can be mobilized and cause corrosion on exposed copper features.  In this follow-on project we would like to develop a Test Method for determining Pitting / Crevice Corrosion capability of a Solder Flux. We then would submit the method to IPC Cleaning and Coating Committee for consideration of an additional test within J-STD 004 to evaluate flux potential to propagate Pitting / Crevice Corrosion capability of a Solder Flux on Cu and Sn and subsequently work with the IPC Committee on Cleanings and Coatings to implement our recommendations.

Project stage: 
Lead company: 

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Idea Information

1. Various forms of corrosion and Electro Chemical Migration failures on products that pass the current cleanliness and corrosion resistance test protocols have demonstrated that these test procedures are not effective.
2. The failure mechanism is the same regardless what segment of the electronics industry the PCBA is used.
3. The current testing does not take into consideration various acceleration factors associated with no clean flux and product design features.
The current industry standard test protocols were originally developed to identify highly ionic contaminant levels (halides) after a cleaning process.  These test protocols are not completely effective at identifying Pitting / Crevice Corrosion from no-clean flux residues

Definition Information

High level objectives: 

From previous experience it is currently accepted that "Activity of flux is one of the important aspects in circuit reliability".  As such our thinking is that we would like to:

  1. Examine CuOx dissolution in flux solutions on Cu substrates using electrochemical methods
  2. Potentiometry  and Gravimetric analysis
  • Sn2+ and Sn4+ can form Sn-carboxylate complete and dissolve into solution
  • Examine the chemistry and kinetics of halide and halide free fluxes at Cu and Sn surfaces
  • Halide free fluxes include carboxylic acids in aqueous or solvent based carriers with several other additives

    Key Participants: 
    i3 Electronics
    Keysight Technologies
    MacDermid Enthone
    Nihon Superior
    RBP Chemical Technology