前言

最(zui)近看(kan)到國(guo)外論壇上關于陶瓷電(dian)(dian)容用于ESD靜(jing)電(dian)(dian)防護的(de)(de)談論，覺得不(bu)錯，分享給大家看(kan)一看(kan)，事情(qing)的(de)(de)起(qi)因是(shi)朱奈德(de)工在(zai)做ESD靜(jing)電(dian)(dian)電(dian)(dian)容選型時，不(bu)清楚(chu)ESD靜(jing)電(dian)(dian)電(dian)(dian)容的(de)(de)額(e)定電(dian)(dian)壓(ya)(ya)是(shi)否(fou)與(yu)此有關，舉個例子，比如說50V額(e)定電(dian)(dian)壓(ya)(ya)的(de)(de)電(dian)(dian)容和100V額(e)定電(dian)(dian)壓(ya)(ya)的(de)(de)電(dian)(dian)容是(shi)不(bu)是(shi)都能用于15KV的(de)(de)ESD防護呢？

問題解讀

電(dian)(dian)容的(de)額定電(dian)(dian)壓(ya)(ya)指的(de)是長時(shi)耐(nai)壓(ya)(ya)，也就是電(dian)(dian)容需(xu)要(yao)長時(shi)間承受的(de)電(dian)(dian)壓(ya)(ya)，比如(ru)掛在5V電(dian)(dian)源(yuan)線上的(de)電(dian)(dian)容，電(dian)(dian)容選型時(shi)額定電(dian)(dian)壓(ya)(ya)必須要(yao)大(da)于(yu)5V才(cai)行(xing)。ESD靜電(dian)(dian)電(dian)(dian)壓(ya)(ya)屬于(yu)瞬態電(dian)(dian)壓(ya)(ya)，雖然電(dian)(dian)壓(ya)(ya)很(hen)高，比如(ru)15000V，但是時(shi)間很(hen)短，不能拿這個額定電(dian)(dian)壓(ya)(ya)去衡量。所以(yi)專家的(de)回答也是說如(ru)果電(dian)(dian)容用(yong)作ESD防(fang)(fang)護(hu)的(de)話，得參(can)考(kao)電(dian)(dian)容的(de)靜電(dian)(dian)防(fang)(fang)護(hu)參(can)數才(cai)行(xing)。

接著專家給了一個實例來說明如何進行靜電電容選型，比如說要達到12KV的ESD防護能力，無論是額定電壓16V的電容，或者是額定電壓200V的電容，都可以實現12KV的(de)ESD防護(hu)等(deng)級，還給了一個表格來說明：

從這個(ge)表格可以看出電(dian)(dian)容(rong)的(de)容(rong)值(zhi)以及封裝會影響電(dian)(dian)容(rong)的(de)ESD耐受電(dian)(dian)壓(ya)，容(rong)值(zhi)越(yue)(yue)(yue)大(da)，ESD耐受電(dian)(dian)壓(ya)就越(yue)(yue)(yue)高(gao)，封裝越(yue)(yue)(yue)大(da)，ESD耐受電(dian)(dian)壓(ya)也越(yue)(yue)(yue)高(gao)，提高(gao)額(e)定電(dian)(dian)壓(ya)本身(shen)并不能(neng)提高(gao)電(dian)(dian)容(rong)的(de)ESD耐受能(neng)力。

總結

需要注意的(de)是MLCC本(ben)(ben)身具有(you)直流偏(pian)置的(de)特性，電(dian)(dian)(dian)容(rong)的(de)實際靜電(dian)(dian)(dian)容(rong)量值(zhi)隨著直流(DC)電(dian)(dian)(dian)壓(ya)的(de)加載而(er)降低，如果(guo)我們選擇的(de)電(dian)(dian)(dian)容(rong)的(de)工作電(dian)(dian)(dian)壓(ya)本(ben)(ben)身比(bi)較接近電(dian)(dian)(dian)容(rong)的(de)額定電(dian)(dian)(dian)壓(ya)，那么(me)其容(rong)值(zhi)可能會降低得比(bi)較多，比(bi)如(ru)Y5V電容(rong)可能會降(jiang)低50%之多，此(ci)時就會大大降(jiang)低電容(rong)的承受能力(li)，這(zhe)一點也是(shi)老外沒提到的，大家在選型時務必要注意。

總(zong)結來說選(xuan)擇陶瓷電(dian)容(rong)用于(yu)ESD靜電(dian)防護時，應重點參考其ESD耐受電(dian)壓參數(shu)，并考慮容(rong)值和封(feng)裝以及額(e)定(ding)電(dian)壓的影響(xiang)。