The analysis is multilayer capacitance of pottery and porcelain (reason of MLCC) leakage of electricity
[introduction] MLCC although the function is simple, but because apply extensively in the electronic product such as the smartphone, once invalidation can bring about circuit to be out of order, the function is abnormal, cause product inflammation even, the safe problem such as explosion, its failure mode must be detected by character the attention that waits for relevant engineer.
MLCC although the function is simple, but because apply extensively in the electronic product such as the smartphone, once invalidation can bring about circuit to be out of order, the function is abnormal, cause product inflammation even, the safe problem such as explosion, its failure mode must be detected by character the attention that waits for relevant engineer.
And in a variety of failure mode, capacitance leakage of electricity (low insulation impedance) it is the commonnest invalidation type, its are main the reason can separate the underlying factor in be production process and the outside element in producing a course.
One, underlying factor
1. Empty Void
What capacitance interior eyewinker volatilizes to form in agglomeration process is empty. Empty meeting brings about the short circuit between electrode and potential and electric invalidation, empty older saying reduces IR not only, still can reduce effective look cost. When electrify, bring about because of leakage of electricity likely empty and local calorific, reduce the insulation property of medium of pottery and porcelain, aggravate leakage of electricity, produce craze thereby, explode, the phenomenon such as combustion.
2. Agglomeration crackle Crack
Agglomeration crackle results from agglomeration commonly cool quickly in the process, in electrode edge appear on perpendicular direction.
3. Statified Delamination
Storied generation often is to be after pile, because of lamination undesirable or platoon glue, agglomeration is inadequate bring about, in the interfuse between layer and layer air, outside impurity and appear dentate transverse craze. Also be different material mixes postheat to expand not to match likely bring about.
2, outside element
1. Thermal shock
Thermal shock basically happens when wave crest solder, temperature changes quickly, bring about capacitance interior break appears between electrode, need to discover through measuring commonly, abrade hind observation, it is lesser break normally, magnifier of need have the aid of affirms, macroscopical break can appear below a few circumstance.
The proposal below this kind of circumstance uses circumfluence solder, or the temperature when solder of slow down wave crest changes (do not exceed 4~5 ℃ / S) , before cleaning face plate control temperature is under 60 ℃ .
2. Outside machinery stress
Because MLCC bases is pottery and porcelain, in place component, cent board, go up in the working procedure such as screw, bring about capacitance probably to get extruding crack greatly too because of mechanical stress, bring about be no longer in force of potential leakage of electricity thereby. Right now break shows oblique line commonly, be in craze from the union of terminal and body of pottery and porcelain.
3. Soldering tin is migratory
Undertake soldering to guide likely calling holding two end below tall wet environment soldering tin is migratory, join brings about short circuit of leakage of electricity to.