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June 2001

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Subject:
From:
Frank Kimmey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 26 Jun 2001 11:38:41 -0700
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Hi again Nicole,
Personally I don't care who the Vendor is (they all have some issues to
worry about and still produce a good product).
But since these are relatively high value, large footprint devices I can
only suggest checking dielectric type (the variable you didn't tell me,
though I will guess Z5U due to your leakage comment), and looking for a
lower height device you could use.
There seems to be some correlation between device thickness and reliability
during processing.
I also think John Maxwell (forgive me John if I'm overstepping here) might
of done some stuff on micro cracks and their effect on leakage.
The effects of thermal shock (even that recommended by the manufacture),
stress of de-panelization, flexure during test, etc. seems to be increased
tremendously on caps that are taller in height than equal value caps of
shorter stature. The micro cracks caused by these stresses could be a part
of your problem.
Hope this helps
FNK

Frank N Kimmey, C.I.D.
Senior PCB Designer
Powerwave Technologies
PH. 916-941-3159
Fax 916-941-3195


-----Original Message-----
From: Nicole Landreville [mailto:[log in to unmask]]
Sent: Tuesday, June 26, 2001 10:10 AM
To: [log in to unmask]
Subject: Re: [TN] Multilayer Ceramic Chip Capacitors Quality


Since Frank and Genny are interested in knowing what type of capacitors we
had encountered problem with and since I believe most of you should be aware
of the following risks: First of all, ceramic multilayers capacitors are
extremely sensitive to high heat. The heat profile temperature is specified
by each manufacturer. As you probably understand, I don't feel comfortable
revealing the manufacturer's name since, as pointed out by Steven, these
manufacturing defects might not be a problem.
We observed random issues with 10 microfarads / case 2220 / for 50 V. The
capacitors we have used often showed leakage after a certain usage.
Also, we observed very constant manufacturing issues with 22 microfarads /
case 3025 / for 50 V. Electrodes are made of silver for both types.
I suspect the reliability of these capacitors is inversely proportional to
size, value and voltage.
Hope this helps more people.
Nicole
-----Original Message-----
From: Frank Kimmey [mailto:[log in to unmask]]
Sent: Tuesday, June 26, 2001 12:14 PM
To: TechNet E-Mail Forum.; [log in to unmask]
Subject: RE: [TN] Multilayer Ceramic Chip Capacitors Quality


Hi Nicole,

Could you give a little more data?
What sizes, dielectric, values?
I have seen many cap issues related to these variables and might have some
suggestions.
Call me if I can help.
FNK

Frank N Kimmey, C.I.D.
Senior PCB Designer
Powerwave Technologies
PH. 916-941-3159
Fax 916-941-3195


-----Original Message-----
From: Nicole Landreville [mailto:[log in to unmask]]
Sent: Tuesday, June 26, 2001 8:37 AM
To: [log in to unmask]
Subject: [TN] Multilayer Ceramic Chip Capacitors Quality


Bonjour a tous!
We have found some internal manufacturing defects in some Multilayers
Ceramic Chip Capacitors. After discovering reliability problems with these
types of capacitors (extreme leakage increasing with time) we have decided
to perform a construction analysis. The type of issues found relates to
misalignment of electrodes, electrode layers varying in length, warping of
dielectric plates. Unfortunately, to be able to find these manufacturing
defect we had to do a caps microsection. Now that we know that these
capacitor are prone to manufacturing defects, I would like to know if there
is any way (processes, low cost equipment or service house) to detect these
defects without scraping or damaging the caps? Originally I was thinking
that these could be X-rayed but I am not sure that the resolution would be
sharp enough. I would really appreciate if anyone could help me with this
important problem.

Thank you and good day!

Nicole Landreville, Eng.
Electrical & Supplier QC Engineer
World Heart Corporation
Ottawa, Ontario

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