Interconnect Stress Testing Resistance Drift Correlation with Multilayer PCB Microsections
Interconnect stress testing detects sub-micron post separations through dynamic resistance drift before static optical microsections show physical cracks.
Resistance Drift
Value Deviation
An electrical instability involves the gradual change in the ohmic value of a resistive component over time or under varying environmental conditions. While all resistors exhibit some variance, resistance drift specifically refers to the permanent or semi-permanent shift caused by material aging or environmental stress. It is measured in parts per million per year or after specific test intervals.
Thermal Influence
High temperatures accelerate the chemical and physical changes within the resistive element or the termination interface. Exposure to moisture or corrosive atmospheres can also trigger resistance drift by inducing oxidation in the thin film layers. When a circuit operates near its power rating, the internal heat generated can cause the value to wander beyond the original tolerance.
Precision analog circuits are particularly sensitive to these fluctuations. Heat changes values.
Longterm Stability
Selection of stable resistor technologies like metal foil or thin film reduces the impact of these changes on system performance. While thick film resistors are cost effective, they typically show a higher resistance drift when subjected to high humidity or thermal shock. Specifying a low drift component ensures that the gain or reference voltage in a critical circuit remains within the design window for the entire life of the product.