Technology |

The failure of the thick film resistor is rarely caused by the malfunctioning of its resistive element, but it is primarily caused by the external environmental factors like electrical and mechanical stresses as well as the handling issues. These failures can be classified as either performance, degradation or complete failure.

Here are the main causes of the thick film resistor.

Mechanical failure

Apart from the damages caused by handling which leads to substrate chips an
d cracks, most of the mechanical damages are caused by excessive vibrations or misalignment/inappropriate mounting of your device. Cracking of your resistor material could be caused by extension/compression or vibration of the resistor caused by the improper mounting. This might lead to a change of the resistor value, component failure or damage of the resistive element.

Environmental factors

Most of the thick film resistors are coated to protect them from moisture and other aggressive chemicals elements. However, the various environmental factors like contamination and moisture must be considered carefully. Both of these could cause migration of the metal between the various terminals of the resistors which could lead to potential short-circuiting or cause a change in the resistance value.

Overload conditions

Continous over-loading of the resistor devices leads to a degradation of the insulation resistance. It might also result in a change of the various parameters or the resistor such as the resistor value over time. Stress or fluctuations in the voltage values can cause electrical conduction in the resitor’s materials which are non-conductors. This could lead to deterioration and occasional failure due to the hot spot generated. It is therefore very critical to observe the resistor’s maximum voltage as specified by the manufacturer.

Thermal stress

Heat mainly propagates most of the mechanical failure modes in the thick film resistor. It is, therefore, imperative that you understand the process of heat dissipation as well as the resistor’s properties and the substrate materials. A low powered resistor is known to dissipate a lot of heat via conduction. Most of this heat is dissipated through its connections or its components leads. A high powered resistor dissipates its heat through the process of radiation. Heat is generated when current flows through a resistor. This further leads to the induction of stress in the resistor.

Surge conditions

The mass of the resistor element determines the surge survivability in the thick film resistor. The power surge is directly proportional to the product of its thickness and the surface area. The resistor’s geometry also affects its surge withstanding capability. Increased surface area in the resistor is useful as it allows more heat to be dissipated reducing the thermal stress.