手机PCB板接地孔原则分析

Analysis on Principle of Cell Phone PCB Ground Hole

手机PCB layout打地孔没有统一的指导原则,打地孔大多是根据以往经验,这导致了手机PCB地孔疏密不一,因此尝试总结PCB地孔间距的最大距离值。首先从空腔谐振理论看,PCB可以认为是由大大小小的空腔组成的,因此根据空腔谐振理论可以找到理论的孔间距最大值;其次从器件地回路计算出回路最大电流值,从而可以得出应该打多少个回流地孔;最后从避免EMI发生的角度上可计算出合适的孔间距值。根据这3个方面总结出了一个PCB接地孔最大间距的最大限度值:PCB板上最大频率的二十分之一波长。

There is no unified guiding principle of cell phone PCB layout ground hole. In general, ground hole is get according to past experiences. It leads to uneven ground hole of cell phone PCB. Therefore, the maximum distance between PCB ground holes was tentatively summarized. First, from the aspect of cavity resonance theory, PCB could be deemed as the composition of cavities with different sizes and the maximum hole distance could be derived from cavity resonance theory. Second, the maximum current value of loops could be calculated according to ground loops to derive the number of ground hole. Third, from the perspective of EMI, which frequency could avoid the occurrence of EMI. According to the synthesis of above aspects, the maximum distance between PCB ground holes is one twentieth of wavelength of the highest frequency on PCB.