# Presentation: 406691

##  Wire-bond failures induced by resonant vibrations in the CDF silicon detector

- Bond with current pulses

- Bond without current pulses

**A closer look with 40500 frames/second video equipment**

**Single frames have been digitized and a quantitative analysis has been performed.**
**Bonds were excited with limited number of pulses to measure the amplitude of the motion versus the number of pulses and the dumping ratio.**

**40 pulses in a row**

**Free decay of the motion**

**Conclusions**

** ****Wire-bond failures induced by resonant vibrations in the CDF silicon detector**

**Time line of the silicon ****integration**** in CDF for RunII**

**Long after the end of commissioning a non negligible rate of permanent failures started to show up. Both failure modes are consistent with loosing the continuity on power lines on the non-accessible part of the detector.**
**DVDD JUMPER connection**
**Loss of the Z side information**
**Wire bonds lying on a plane that is orthogonal to the magnetic field**
**DOIM power connection**
**Loss of all information from the module**
**Wire bonds lying on a plane that contains the B Field vector but have a step up from a substrate to the other**
**These are not the wire-bonds with the largest current in the system!**
**Current surges (fusing the bond) were ruled out**
**Aging mechanisms were ruled out**

**JUMPER route control, power and data between r******** and rZ sides of the double sided SVXII modules.**

**DOIM are laser diodes packages that drive data from the tracking volume to the VME crates.**

_**AVOID**_** trigger conditions that could resonate the bonds.**
**Administrative and Run-Control software.**
_**Understood and removed**_** all possible spurious sources of the 5****th**** L1A**
**TS (Trigger Supervisor) firmware and Command Signal strength changes**
_**Current swing minimization**_
**Reduce the power**
**   ****output of the **
**   ****bus drivers**
**Minimization of**
**    ****noise occupancy**
_**Trigger Inhibit on resonance**_** ****(in place and being commissioned)**

**CDF operational response**

| A perfect
Wire-bond | While resonated
a crack grows 
at the heel | The bond breaks on a time scale of minutes |
| --- | --- | --- |

**Wire-bonds break due to fatigue stress on their heel induced by resonant vibration. These resonant vibrations are a direct consequence of the oscillating Lorentz forces induced by the magnetic field on wire-bonds with non-DC current. **

**Resonant frequencies**

**2-3 natural resonant frequencies up to 50 kHz (range of interest for CDF) for realistically shaped bonds.**
**Each resonant frequency f can be excited with pulses at f, f/2, f/4 etc**

**The resonant system has a very high Q. **
**The width of the resonance is about 1-200 Hz.**
**Differently shaped bonds imply different resonant frequencies.**

**Last fall the CDF experiment faced a crisis due to internal unrecoverable failures on the silicon detector. **
**The source of the failures has been understood to be simple physics mechanisms that could have been taken into account during the design and construction of the hardware.**
**Counter measures have been studied, developed and applied to the CDF experiment. Since these implementations are in place, no other failures have occurred.**

- Gino Bolla, Purdue University for the CDF RUN2 Silicon Group

- 9th Pisa Meeting, La Biodola, Elba Italy, May 25-31

**Small drops of encapsulant**** **
**(**Sylgard 186 Silicone Elastomer from Dowcorning) **limit the oscillation amplitude by more than a factor of 50 by covering just the first **
**50-100 ********m of the wire.**
**We were not able to break these wire-bonds!**

**Not real encapsulant**