Anti-Surge High-Power Thick Film Chip Resistors for Extensive PCB Protection

Surge protection has become increasingly important for modern electronics as the footprints of surface mount device (SMD) devices continuously shrink and high-speed multi-layer PCBs are widely used. As the most used components on a PCB, chip resistors demonstrate as the weakest entry point of high-peak short-duration surge and pulses in events of electrical failures. In situations when large instantaneous current (e.g. inductive transients, load dump, power charging/discharging, inrush current or ESD (Electrostatic Discharge) events) is likely to be applied, the chip resistors will be more vulnerable than other type of passive components. Chip resistors are typically low power rated at no more than 1/10 W. When a surge is induced on the resistor, it means an overload condition of pulse type – high energy and long duration, or an overload condition of surge type – high power and short duration. To absorb the excessive surge energy to avoid fire, damage and unexpected circuit behaviors, chip resistors that are capable of act against high energy surges and pulses must be used.

The diagram shows the typical characteristics of a high-power short-duration surge and a high-energy long-duration pulse.

Rohm Semiconductor ESR series Anti-surge chip resistors are manufactured with exclusive resistive element pattern and laser trimming technology to provide superior anti-surge characteristics. They are rated for 2kV to 5kV ESD resistance. The SDR03 series anti-surge thick film chip resistors have superior power rating of 0.3W in 0603 size for ambient temperatures up to 70 C. When the ambient temperature is above 70 C, power dissipation derates to 0.25W up to 105 C. Test data shows the anti-surge high-power resistors have excellent performance under overload stress indicated by the below figures that shows nearly constant resistances for all values at 2kV, 3kV and 5kV respectively.

Anti-surge characteristics for ESD test – Rohm ESR 01 & 03 vs. Rohm Standard MCR chip resistor (Resistance change ratio w.r.t resistance under applied voltage)
Test conditions: Anti-surge characteristics for ESD test – Rohm ESR 01 & 03 vs. Rohm Standard MCR chip resistor
Structure of Rohm High-Power SDR Anti-Surge Thick Film Chip Resistor

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