TCXO Failure Analysis
7 days ago
- #Hardware Debugging
- #TCXO
- #Failure Analysis
- The ThunderScope PCIe card prototype had a TCXO failure causing a 6.6% slower timebase.
- Initial troubleshooting revealed the PLL wasn't locked due to a flatlined 10 MHz TCXO output.
- Replacing the TCXO fixed the issue, but the root cause was investigated further.
- The TCXO (Temperature Compensated Crystal Oscillator) compensates for thermal drift in quartz oscillators.
- Ultrasonic cleaning was suspected as a potential cause due to resonance risks with MEMS and oscillators.
- Depackaging the TCXO involved grinding and machining the metal lid without damaging internal components.
- Visual and electrical inspection showed the quartz crystal was intact and resonating at 20 MHz (implying a divide-by-two in the driver).
- The failure was traced to a broken crescent bond wire connecting the controller die to the quartz crystal.
- Poor wire bonding process control and ultrasonic cleaning likely contributed to the bond wire failure.
- A second similar failure post-ultrasonic cleaning supports the conclusion.