Undetected wire bond defects can cause intermittent electrical faults or rapid degradation over time. Many wire bonding failures are subtle and cannot be detected using electrical curve trace analysis. For instance, wire bonds may not be properly attached, but once encapsulated, they can still make contact with the bond pads due to compressive forces from the mold compound, allowing them to pass electrical curve trace analysis.
Further analysis of decapsulated samples can reveal subtle bonding defects, but such analysis is involved and time consuming. When samples are decapsulated using MIP, rather than acid or CF4 plasma, even minor binding defects can be identified by simple inspection under an optical microscope.
Case study: electrically failing PCC sample
An electrically failing palladium-coated copper (PCC) wire bonded sample was decapsulated using MIP. Curve trace analysis indicated that several wire bonds were not attached. Optical inspection of the sample revealed that the wires identified to have bonding defects appeared dark brown in color and had a rough surface, showing signs of oxidation.
SEM images also confirmed that these wire and their underside had significantly rougher surfaces than wires that were properly bonded.
How JIACO Instruments’ MIP etching reveals bonding defects.
As JIACO’s O2 MIP locally etches a sample by scanning over a defined path, the surface of the sample is heated by the plasma effluent, while the bulk temperature remains low. At elevated temperatures, oxidation occurs more readily. Wires with bonding defects, such as ball bond lift, dissipate heat less effectively than properly bonded wires. As a result, these defective wires are more prone to oxidation during processing. Therefore, wires showing signs of oxidation can be easily identified to have bonding defects, even if they passed curve trace analysis, while wires with smooth, shiny surfaces can be identified as properly bonded.
This unique application enables faster root cause analysis of bonding defects, as visual inspection with optical microscopy is often sufficient to identify all bonding defects within a sample.
Interested in learning more about how MIP decapsulation can reveal subtle bonding defects? Download the paper here:
https://lnkd.in/eMfqCKm7
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