下面是Fanessay提供的一篇essay范文--MLCC breakdown cause,这篇论文主要讨论的是MLCC击穿的原因。现在，世界在进步，人类在进步，科技发展速度快，MLCC慢慢变成了整个世界上发展速度最快和用量最多的片式原件，并且在很多行业中得到应用，也是因为这样，导致MLCC在运行中可能会出现击穿现象。在高电压下，MLCC超出所能承受的范围，就可能会被击穿。面对这种问题,应该采取措施，可以运用叠加原理，减少电场的叠加量，进一步降低强度，从而减少击穿现象的出现。
As is known to all, at this stage in the development of times, the dosage of MLCC development gradually became the world's largest and fastest growing electronic component, is widely used in many industries, such as household appliances, communication equipment, etc., it is because the element of application scope is widespread, so prone to MLCC in overall breakdown phenomenon, seriously affecting the effects of application. In order to further improve this phenomenon, to explore the reason of MLCC breakdown, requires the analysis and discussion from various angles, such as materials, production process and so on, therefore this article based on the study of others, for some ideas to give new theory, breakdown reason of MLCC, help for production and application in the future.
MLCC there are three main parts, including the outer electrode, the electrode, dielectric ceramic, generally speaking, in MLCC internal appear alternately stacked phenomenon, the most representative is the metal electrode layer and ceramic dielectric layer, however, from another perspective, in unity within the metal electrode layer, if one side and the outside electrode contact each other, then the other side will be in the ceramic medium, can't and the outside electrode connected to each other. And is usually within two adjacent metal electrode and ceramic media together to form a parallel plate capacitor, this design is more subtle, obvious effects in the continuous automatic production, and according to the practical study shows that this model can also promote electric capacity of unit volume. However, from another perspective, it is because the structure characteristics of MLCC, so the edge electric field are prone to distortion, serious when still can lead to the metal electrode current distribution presents the uneven phenomenon. If the cause of this phenomenon comes from the material and processing, the later stage will produce breakdown in the material, unable to play the role of MLCC, or even lose its role and value.
If you want to understand the cause of the breakdown of MLCC, priority is the analysis on the breakdown model, at the present stage MLCC breakdown model mainly includes two kinds, one is the breakdown voltage, breakdown, the second is current from the analysis on basic properties, the breakdown voltage and the current law of breakdown is different, the physical process is not the same, the differences between the two, of course, in the research in recent years, there are other breakdown pattern, but less likely, such as electric breakdown, mainly because the dielectric layer is thinner, capacity is larger.
From the perspective of the physical properties of the so-called breakdown mainly refers to the electric field under the action of capacitor voltage sudden breakdown voltage breakdown, the principle of voltage breakdown happens is because the free electrons in a capacitor medium affected by the action of the strong electric field and, with the neutral molecules collide, so will form a new free electrons, especially in ionization often lead to the happening of the electron flow, causing the breakdown. Voltage breakdown occurs during the temperature is not high, low dielectric loss, the internal structure of uniform, but the late research voltage breakdown has nothing to do with temperature, time, and micro structure, medium thickness, electrode area instead. From another perspective, the cause of MLCC occurrence breakdown is not only include the following points, also with the edge of the electric field distortion has the close relation, in which the distribution of electric field as shown in figure 1. In the left side of the, A, B two near the two metal electrodes in A parallel state can be regarded as the most basic plate capacitor structure; On the right side of the A and B two points, as the short electrode, at point A metal electrode layer will block, cannot be associated with the outside electrode, it is this imperfect structure will lead to the distortion electric field. If according to figure 2 were analyzed, and then gaussian closure can form a cylinder surface, one of which is for the rectangular cylinder, the other is a trapezoidal cylinder, both up and down the floor with metal electrodes are in balance.
Needless to say, each capacitor has the power consumption, including MLCC is mainly to form thermal electricity, one of the part is exchanged with the environment, can let capacitance fever in another part, the temperature was increased, which under normal circumstances, condenser of heat energy, smaller than the heat emitted only so can guarantee the stability of capacitance work under hot condition. If the effective value of current is larger, so the heat energy leads to capacitor which, over time, heat will form the accumulation, will lead to the temperature inside the capacitor to get higher, the corresponding dielectric loss will be increased, can cause damage to internal dielectric ceramic layer and influence. It is understood that the breakdown caused by excessive current is mainly used in RF circuits. , of course, is fundamentally to avoid the effects of current breakdown, can in the design, the author thinks that, the first is to reduce as far as possible the MLCC equivalent series resistance, the second is to fundamentally guarantee CMLCC metal electrode current in the load capacity.
Which need to be considered is the particularity of the internal structure of MLCC have, because the electrode current distribution is not equal, load intensity is not the same, in figure 3 two adjacent inner electrode can prevent branch capacitance and can also form a bypass capacitors in parallel, if the total current flowing into the MLCC is I, then is split down the current I / 7, and for close to the outermost two electrodes within the load current for I / 7, in the innermost layer of the electrodes, each carrying two branch capacitance current, electrode can be used 2 I / 7 said. In addition, if the same root electrode, if current is flowing from left to right, so in the beginning the greatest electrode current is connected to the left, and if in a constant, then the corresponding inner electrode current will be reduced gradually, even formation law of sandstrom, namely the right results, so the electrode current load.
Through the above analysis of the breakdown voltage and current breakdown can learn if uniform in MLCC internal ceramic media, under the condition of zero defect, so the conclusion can include the following: the first is to apply high voltage MLCC, if beyond, so prone to breakdown, in addition to the interior distortion electric field MLCC, if the field intensity at point A of figure 1 is high, so in figure 1 AB two breakdown takes place, in this case strictly according to the superposition principle of electric field, select the appropriate size decrease distortion of electric field superposition, thereby reducing strength, improve the ability of fight against wear. If because current overload, the second is caused by the failure, the main reasons is because the current distribution is not uniform, occurs in the inside layer of the electrode, and a case within the outer electrode and electrode integration, will appear current breakdown phenomenon, resulting in capacitance failure.
Essay范文:MLCC breakdown cause 2018-04-17