Gold Embrittlement Mitigation

What causes gold embrittlement?

Many electronic components and connector leads are plated with gold because gold:

• Resists corrosion and oxidation
• Provides excellent electrical conductivity
• Improves contact reliability

However, during soldering, the gold plating dissolves into the molten solder. If too much gold enters the solder joint, it reacts with tin to form brittle gold-tin intermetallic compounds, primarily:   AuSn4

Why is this a problem?

A good solder joint should absorb:

• Thermal expansion
• Vibration
• Mechanical stress
• Shock loading

Gold embrittled joints lose ductility and can crack under stress.

Typical failure modes include:

• Cracked solder fillets
• Intermittent electrical connections
• Open circuits
• Early fatigue failure
• Fractures during vibration or thermal cycling

This is especially dangerous in:

• Military electronics
• Space systems
• Aircraft avionics
• Medical implants
• High-vibration environments

Where does it commonly occur?

Gold embrittlement is most likely when:

• Thick gold plating is used
• Leads/connectors are not properly de-golded before soldering
• Small solder volumes are used
• Rework adds repeated thermal cycles
• Fine-pitch/high-density assemblies are present

Common risk areas include:

• Connector pins
• Relay contacts
• Hermetic packages
• Hybrid microcircuits
• RF/microwave assemblies
• High-reliability PCB assemblies

LED with Au Plating
(Showing Embrittlement)

LED with Sn/Pb Solder Termination
(Post GEM processing)

 
QFN-24 with Gold (Au) Termination Finish
(Showing Embrittlement)

QFN-24 with Sn/Pb Termination Finish
(Post GEM Processing)