Ioan, As you can tell from all the responses ceramic capacitor cracks are problematic. Thermally induced cracks if they are large enough can seen or detect them with x-ray or acoustic microscopy provided they aren't in the termination area where there is a curved surface. John Maxwell's advice about not touching a ceramic capacitor with a soldering iron is good advice. You'll do nothing but induce more problems. The real problematic cracks are mechanically induced "Flexure Cracks". They happen when mechanical stress during operation like de-panization, insertion of press-fit connectors, mounting screws, handling, or other operations are exerted on attached capacitors. The stress concentration is highest at the inside edge of the capacitor termination. Since this is area is under the capacitor you can't see the crack. The flexure cracks propagate upward and outward. If the crack doesn't propagate across adjacent electrodes in the capacitor they are benign. Even if they do propagate across adjacent electrodes, when capacitors crack they "crack open". The internal electrodes aren't short-circuited. The parallel plate area removed by the "open" is typically small and not detectable by capacitance measurements. So big deal, why care if you can't see them or detect these small cracks using acoustic microscopy. Your product should pass test and work. The horrible nature of "flexure cracks" is that they are a reliability issues that can cause problems during use. Without a crack the electrodes are separated by the ceramic dielectric. However, the crack provides a path between adjacent electrodes. The dielectric in the crack is now air instead of ceramic. You can detect these cracks using THB (i.e., Temperature Humidity Bias) techniques but it is difficult to monitor and find very small leakage currents and they need to be done insitu. If you take capacitors out of a THB chamber and test them externally what typically happens is you apply a measuring voltage and there may be an increased leakage current when the measuring voltage is apply but this leakage current causes a local heating in the crack that drives out the moisture in the crack causing an increase in dielectric and the leakage current stops and is no longer detectable. Back in 1987 when I participated as a member of the AT&T "Crack Busters" Team we had a serious problem with products being returned with "blown" capacitors. They were typically high capacitance 1812 size ceramic capacitors used as by-pass or filtering capacitors across 24 or 48VDC power supplies or regulators. What we learned was that we induced "flexure cracks" during manufacturing and handling that were not being detected and worked as long as the humidity in the environment was relatively low. However, whenever our products were in and environment where the humidity would increase (e.g., thunder storm, rain shower, or even a janitorial service mopping the floors next to operating equipment) the 24 or 48VDC applied power would short-circuit in the "flexure crack" causing the capacitor to blow-up. Out of this work came the use of humidity to find crack capacitors. We'd put products in 85C/85%RH (no bias) for 24 hours to inject humidity into the crack and then take the products out of the humidity chamber an immediately turn them on (i.e., apply the 24 or 48VDC). The instantaneous current draw between electrodes in the crack would cause the capacitors to blow-up. There were any times when we didn't want to wait 24 hours so we hurry the process by putting the product in boiling water for 30 minutes. I won't suggest using the humidity/power/blow-up technique as a process quality screen for "flexure cracks" because when capacitors do blow-up they usually cause PCB damage. However, this technique is effective in finding out that you have a flexure crack issues and allows one to determine if product/process modifications are effective in eliminating "flexure cracks". Sorry for the long winded answer. Regards, George George M. Wenger, Andrew Corporation Reliability / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan Sent: Monday, June 05, 2006 2:22 PM To: [log in to unmask] Subject: Re: [TN] Finding cracked capacitors So dear colleagues, there is not much I can do with a plain thermal shock or thermal cycling. I absolutely need humidity too. Bad news, I am not equipped for that. George, the boiling water thing is interesting. What do you mean by "put a power supply across them", connecting a certain voltage or amperage directly to the terminals of the caps? 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