Short answer

Minimize gold plating thickness on PCB pads and component leads when using SnAgCu solder to mitigate the risk of gold embrittlement and ensure long-term joint reliability.

Field: Final Production
Source: Academic Publication (2011)
Method: Experimental analysis
Sample: 40 boards
Evidence: Strong effect

The presence and concentration of gold in SnAgCu solder joints, particularly in conjunction with nickel plating, accelerate the formation and growth of detrimental intermetallic compounds (IMCs) that can lead to premature joint failure. This final production research insight is drawn from a 2011 study published in Academic Publication. Using Experimental analysis with 40 boards, researchers explored how this design variable affects real-world outcomes. The key design takeaway: Minimize gold plating thickness on PCB pads and component leads when using SnAgCu solder to mitigate the risk of gold embrittlement and ensure long-term joint reliability.

Study

Final ProductionHigh ImpactStrong effect

Gold content in SnAgCu solder joints significantly impacts intermetallic compound formation and fracture susceptibility

Academic Publication · 2011

Key Findings

01Gold in solder joints promotes the formation and growth of intermetallic compounds (IMCs) like AuSn4.
02IMCs migrate to component and board interfaces, and fracture often occurs within or along these IMC layers.
03The presence of nickel alongside gold exacerbates the formation of specific IMCs, such as (Cu1-p-qAupNiq)6Sn5 and (Au1-xNix)Sn4.

Application

Design takeaway

Minimize gold plating thickness on PCB pads and component leads when using SnAgCu solder to mitigate the risk of gold embrittlement and ensure long-term joint reliability.

How to apply

When designing or specifying electronic assemblies, consult material specifications for surface finishes and solder alloys. Conduct accelerated aging tests to validate the reliability of chosen materials under expected operating conditions.

Project actions

01When researching materials for a design project involving soldering, investigate the impact of surface finishes on solder joint integrity.
02Consider how different plating materials (like gold and nickel) interact with solder alloys.

Method & Evidence

AimTo investigate the effect of varying gold content on the microstructural evolution and reliability of SnAgCu solder joints during isothermal aging.

MethodExperimental analysis

ProcedureIntegrated circuit packages with different gold coating thicknesses were assembled on printed circuit boards with varying gold over nickel finishes. Samples were subjected to isothermal aging at 125°C for up to 56 days. Microstructural characterization using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) was performed on cross-sectioned solder joints to analyze intermetallic compound formation and elemental composition. Mechanical reliability testing was also conducted.

Sample40 boards

ContextElectronics manufacturing, surface finishes for printed circuit boards, solder joint reliability.

Variables

IVGold content in solder joints (influenced by surface finish thickness).

DVMicrostructural evolution (IMC formation and growth), fracture location and susceptibility.

CVSolder alloy composition (SnAgCu), aging temperature (125°C), aging duration.

Strengths & Limitations

Strengths

+Direct experimental investigation of gold's effect on SnAgCu solder joints.
+Use of advanced characterization techniques (SEM/EDS) for detailed microstructural analysis.

Limitations

The study's findings are specific to the tested SnAgCu solder and gold plating conditions. Real-world operating conditions may introduce other variables affecting solder joint performance.

Reliability & validity

The study's reliability is supported by the use of standardized characterization techniques (SEM/EDS) and controlled experimental conditions. Validity is enhanced by investigating both microstructural changes and mechanical reliability testing.

Think critically

How might the findings regarding gold embrittlement in SnAgCu solder joints be extrapolated to other lead-free solder alloys, or what new research questions arise from these observations?

Design Principles

"Control of interfacial metallurgy is critical for the long-term performance and reliability of soldered electronic assemblies."

Understanding the interaction between gold plating and lead-free solder alloys is crucial for ensuring the long-term reliability of electronic assemblies. Designers and manufacturers must carefully consider surface finish specifications to prevent embrittlement and ensure product longevity.

What This Means for Your Design

Too much gold on electronic parts can make solder joints weak and break easily, especially over time and with heat.

How to use in your project

1.Reference this study when discussing the selection of materials for PCB assembly or component mounting, particularly concerning surface finishes and their impact on solder joint reliability.

Add to My Project

Quick Cite

Paragraph starter

Research indicates that the gold content in solder joints significantly influences their microstructural evolution and reliability. Specifically, the formation and growth of intermetallic compounds (IMCs) are accelerated by gold, leading to potential embrittlement and fracture, particularly when nickel is also present as a plating layer. This highlights the critical need for careful material selection in electronic design to ensure long-term product performance.

Source

Academic Publication

Effect of Au Content on Microstructural Evolution of SnAgCu Solder Joints that Undergo Isothermal Aging and Reliability Testing

journal · 2011

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Questions About This Research

What does the research say about gold content in snagcu solder joints significantly impacts intermetallic compound formation and fracture susceptibility?: Minimize gold plating thickness on PCB pads and component leads when using SnAgCu solder to mitigate the risk of gold embrittlement and ensure long-term joint reliability. Evidence: Academic Publication (2011).
Why does "Gold content in SnAgCu solder joints significantly impacts intermetallic compound formation and fracture susceptibility" matter for design?: Understanding the interaction between gold plating and lead-free solder alloys is crucial for ensuring the long-term reliability of electronic assemblies. Designers and manufacturers must carefully consider surface finish specifications to prevent embrittlement and ensure product longevity.
How can designers apply this research?: Minimize gold plating thickness on PCB pads and component leads when using SnAgCu solder to mitigate the risk of gold embrittlement and ensure long-term joint reliability.
What were the main findings?: Gold in solder joints promotes the formation and growth of intermetallic compounds (IMCs) like AuSn4.. IMCs migrate to component and board interfaces, and fracture often occurs within or along these IMC layers.. The presence of nickel alongside gold exacerbates the formation of specific IMCs, such as (Cu1-p-qAupNiq)6Sn5 and (Au1-xNix)Sn4.
What research method was used?: Experimental analysis with 40 boards.
How strong is the evidence?: Evidence strength is rated Strong effect, based on a 2011 journal from Academic Publication.
What should I do differently in my next project?: When designing or specifying electronic assemblies, consult material specifications for surface finishes and solder alloys. Conduct accelerated aging tests to validate the reliability of chosen materials under expected operating conditions.
What are the limitations?: The study focused on specific SnAgCu compositions and aging conditions; results may vary with different solder alloys or operating environments. The exact acceptable gold limit for lead-free solder joints remains less understood than for tin-lead solders.