Murata has not provided us with that bit of information. They will only
tell us that we're not to exceed 275 degrees C for a maximum of 4
seconds.
We've ran experiments at much higher temps and exposure times and have
yet to destroy a component. That's why it's so hard for me to believe
that our standard repair process is responsible for the failure...
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Honsowetz, Eric
Sent: Thursday, April 24, 2008 10:13 AM
To: [log in to unmask]
Subject: Re: [TN] Crystal Damage Question - Failure Mode
Just wondering what temperature would the crystal withstand before it
depolarized...? Perhaps Murata could provide this information.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, April 22, 2008 1:50 PM
To: [log in to unmask]
Subject: Re: [TN] Crystal Damage Question - Failure Mode
If the original rework was due to an electrical test failure such as
would be seen if some other component failed, the crystal may have been
electrically overstressed. In that case, the assembly may still contain
the issue that caused this to happen. The rework may have been
incidental, but possibly the voltage or current overstress is what
caused the original component to fail, not necessarily the heat from the
rework. You may wish to check the assembly to see if a wrong value cap
or resistor was installed in the same (driver) circuit as the crystal
location that was replaced and failed again.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, April 22, 2008 12:26 PM
To: [log in to unmask]
Subject: Re: [TN] Crystal Damage Question - Failure Mode
Folks,
I just went over the vendor's analysis report. In it, we were told
that:
"The crystal failed to oscillate in the initial check. The
impedance-phase characteristics were checked, and we confirmed the
impedance response was small due to the anti-resonant point being close
to the resonant point. We confirmed that the piezoelectric
characteristics became bad, and such were caused by depolarization.
This can be caused by the application of excessive heat. Had this
condition been present before shipment, our electrical characteristics
sorting process would have been rejected this component, so we think the
failure was caused after shipping from Murata."
That's all the info I have.
Thanks again for your help.
Leland
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Tuesday, April 22, 2008 12:26 PM
To: TechNet E-Mail Forum; Leland Woodall
Subject: RE: [TN] Crystal Damage Question
Was the crystal open, exhibiting wrong frequency, shorted, or what? Was
there any test analysis/troubleshooting data?
We need that in order to hazard a guess as to how the rework may have
affected the part or suggest a failure analysis strategy.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, April 22, 2008 10:16 AM
To: [log in to unmask]
Subject: [TN] Crystal Damage Question
Technetters,
We recently had a Murata SMD crystal to cause a failure in the field.
This particular unit had been to Repair and the component was manually
replaced during the manufacturing process.
The vendor analysis reported the component saw excessive heat during the
rework and caused internal depolarization which led to failure.
We made 10 attempts to re-create this condition and were unsuccessful in
doing so. We used dual soldering irons, had the temps cranked as far as
they would go, and gave them excessive exposure times.
Could the vendor analysis have been incorrect, or was their explanation
a real possibility?
Why were we not able to replicate this?
Thanks in advance,
Leland
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