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June 2006

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Subject:
From:
Guenter Grossmann <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Guenter Grossmann <[log in to unmask]>
Date:
Tue, 6 Jun 2006 13:00:19 +0200
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Victor

Sure.

The solution absorbs  X- ray and penetrates readily in small cracks. However, it also penetrates underneath the component. This means that after applying the solution the entire capacitor looks pretty dark. We use the effect that the liquid evaporates easier from underneath the component than in the crack (does not work with hand soldered devices since in this case everything is blocked with flux residues and no B-I solution can penetrate into the crack). With other words, we apply the solution, start looking at the specimen as fast as possible and watch how the picture is getting brighter. Usually the solution in the crack stains the x- ray picture some seconds longer than the one underneath the components. Quite tricky and often we have to repeat the procedure to become confident about the results. And as I said we are not always successful. Mostly the 3 methods are used one after the other to get the puzzle together.

Best regards

Guenter




 

EMPA
Swiss Federal Laboratories  for Materials Testing and Research
Centre for Reliability
Guenter Grossmann,  Senior Engineer

8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :     xx41 1 823 4054
mail:     [log in to unmask]

>>> [log in to unmask] 06.06.2006 12:44:58 >>>
Can you elaborate some more on item 3 with the Boron-Iodine solved in
methylene.....

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guenter Grossmann
Sent: Tuesday, June 06, 2006 2:42 AM
To: [log in to unmask] 
Subject: [TN] Antw: [TN] Finding cracked capacitors

Ioan

We use 3 technologies to search cracks in ceramic caps:
   1. Ultrasonic microscopy. Works pretty well if the cracks are not too
close to the termination and if the structure of the caps is not too
inhomogeneous. Otherwise you don't have a flat surface to couple the US
into the component or the signal noise ratio ist too bad.
   2. Infrared microscopy. Only applicable if you have a connecting path
in the crack where you can pump some power though. I already thought
once that using a penetrating material with a certain conductivity could
help in this measurement but I didn't have the time to look at that in
depth.
   3. X- Ray. Works with a penetrating liquid that absorbs X-Rays
(Boron- Iodine solved in methylene). However, you need to work with
100kV and a detector with a good energy resolution and whenever possible
12bit graphics since the ceramic of the caps is already absorbing a lot
of the X- rays. Plus some tricks in handling.

And its still not sure that we find the bastards.


Best regards

Guenter





EMPA
Swiss Federal Laboratories  for Materials Testing and Research Centre
for Reliability Guenter Grossmann,  Senior Engineer

8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :     xx41 1 823 4054
mail:     [log in to unmask] 

>>> [log in to unmask] 05.06.2006 16:11:04 >>>
Hi Technos,

a never ending story, ceramic caps that crack, possibly due to
depanelizing. The damage is not visible, unless the cap is cross
sectioned.

Is there any testing, thermal cycling or something like that, that could
show the damage real fast?

Thanks,

Ioan



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