ESD problem...
 

since last two months we have experinced a strange incident, that the handset, mostly Nokia brand, entered into the service centre get damaged itself, without any repairing or opening. Even hand set with SIM and batt. ie, in the most working state become damaged within one hour, if it entered into the room. While cheking the PCB of the device showes short circuit at the batt. terminal, and in the most cases, power ics are get damaged. About 25 handsets were found damaged in the same manner within 2 months. Sir please give a reason for this problem..... Is it dueto any ESD or EMI effect? there are two mobile towers located about 200m away form our service centre.