Cyanoacrylate Debonding on Aluminum-ABS Assembly

Summary

A consumer electronics manufacturer experienced widespread bond failures in an aluminum-to-ABS plastic assembly. Bonds that initially passed quality testing began failing within 2 weeks of production, with clean separation at the aluminum interface indicating adhesive failure rather than cohesive failure.

Root Cause

Root cause analysis revealed two contributing factors: (1) Residual oils from the aluminum stamping process were not fully removed by the solvent wipe step. The IPA wipe was insufficient for the specific machining lubricant used. (2) Thermal cycling during product use (-10°C to 60°C) created differential expansion stress at the bond interface, exploiting the weakened adhesion.

Solution

Implemented a three-step surface preparation protocol: acetone degrease → IPA wipe → plasma treatment. The plasma treatment activated the aluminum surface and improved wetting. Additionally, switched from rigid CA to a toughened CA formulation (Loctite 480) to accommodate thermal expansion mismatch. Post-fix bond strength increased from 1,200 PSI to 2,800 PSI with zero field failures over 6 months.

Lessons Learned

• •IPA alone is often insufficient for removing machining oils — verify with water break test.
• •Thermal cycling testing should be mandatory for any assembly with CTE mismatch >5 ppm/°C.
• •Toughened CA formulations provide significantly better fatigue resistance than standard CA.
• •Plasma treatment is cost-effective at scale and dramatically improves adhesion to metals.