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Battery powered compaund sealed RF device - how to prevent leakage current?

Oleg Pushkarev
Expert 1740 points
Other Parts Discussed in Thread: CC1190

Hi,

My customer produced a fully sealed sensor board based on CC430+CC1190. It is battery power device with 5 uA current consumption. 99% of the time sensor is in sleep mode. Expected battery life time is about 10 years.

In field testing reveals a problem - quick battery discharge. Some devices drain battery in 2-3 months.

Customer internal investigation shows that problem arose (probably) from bad compound quality. Used compound intended for electronics, nevertheless it seems that exactly compound responsible for high leakage current.

I would appreciate for any suggestions - what should be taken into account for PCB encapsulated in a mold compound (recommendation and precaution)?

Br, Oleg

  • 0
    Guru 735685 points
    According to my experiences, this kind of power consumption problems is usually caused by SW. You should check if your SW would turn on TX or RX and don't turn it off accidentally or you might not let MCU enter low power mode under some cases.
  • 0 in reply to YiKai Chen
    Expert 1740 points

    Hi,

    It's not the case this time. All PCB had inspection before filling compound. The software is working correctly, the module consumes uA in sleep mode.

    During failure investigation customer did a simple test: compound was removed locally around the drained battery. New battery was connected and device continues to work properly. BUT now the sleep current was about 1 mA. And it was possible to locate the exact place where leakage occurs. The leakage spots were discovered in various places - under capacitors ans under MCU. Leakage stops after removing components and PCB cleaning.

  • 0 in reply to Oleg Pushkarev
    TI__Guru**** 317180 points
    I don't have any previous experience with compounds. In this case it sounds like the compound is slightly conductive and/ or change the impedance on the external components/ matching network.