Electro-Chemical Migration

Much of the Assembly industry has experienced the effects of Electro-Chemical Migration.  It has been shown that contaminants on the surface of PCBs can migrate and cause creep corrosion and/or shorts.  This occurs primarily on the newer Pb free surfaces/finishes.  It is thought to be driven by changing geometry, surface finishes and board cleanliness.

Project stage: 
Lead company: 
Kyzen

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Idea Information

Background: 

 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.
 
4   Pitting/Crevice corrosion has been detected on field failed boards
Boards were soldered with a no-clean wave or selective soldering flux
The failure is an open surface type corrosion event
Occurs on boards exposed to
      • Harsh environments
      • Atmosphere pollutants

 

  • High humidity levels
Problem: 

 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 ECM exposures from no-clean flux residues.

 

Intermittent defects in soldermask provide potential failure locations
May expose a copper trace
Wave and Selective Solder Processes
Deposit liquid flux over the surface being soldered
No-Clean processes
Flux residue is not removed after soldering
Flux is formulated to have a non-ionic (benign) residue
The problem
Active flux can be wicked into openings or flaws in the soldermask
Active flux can propagate corrosion onto exposed metals
Ions from the flux residue can be mobilized with atmospheric moisture
 

 

Definition Information

Goals / Benefits: 
To identify the required enhancements to the current industry specifications, test methds and coupon designs, to midigate the Electro-Chemical Migration and corrosion induced failures when no-clean fluxes are used.
 
 
Approach: 
  • Planning Steps: 9/12/12
    • List current test methods / etc.
    • List failure modes
    • Correlate failures to gaps in test methods
    • Identify modifications required to test methods
    • Develop DOE’s to validate proposed changes
    • Perform DOE’s. 
    • Collect and evaluate test data
    • Draft proposed changes to test methods / etc.
    • Provided proposed changes and supporting data to IPC, JEDIC, etc.
    • Write final report

 

 

 

 

 

 

 

 

 

Key Participants: 
Celestica
Ciena
Cisco
Dell
Engent
Flex
Fujitsu
Huawei
IBM
Indium
Isola Group
Juniper
Keysight Technologies
Kyzen
Nihon Superior
NVIDIA
Oracle
Panasonic
Park Electrochemical
Plexus
Sanmina
Senju Comtek
Shengyi
TTM Technologies
Public