Resistor Trimming Hybrid Current Laser Trim Stability
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Solution Overview
Problem
Current resistor trimming methods, such as current trim and laser trim, face limitations in achieving high precision resistors as they either reduce absolute resistance or fail to stabilize resistance effectively against power and temperature variations.
Innovation Solution
Combining current trim and laser trim techniques to iteratively adjust the resistance of resistors, using a first laser trim to increase resistance above a target value, followed by current trim to achieve near-zero power coefficient of resistance (PCR) or temperature coefficient of resistance (TCR), and optionally a second laser trim to fine-tune the resistance to the target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current trim is applied to stabilize resistance, then power coefficient of resistance is reduced, but absolute resistance decreases
Solution Approach 1:
The patent combines current trim and laser trim processes into a hybrid trimming approach. Current trim is applied first to reduce the power coefficient of resistance and stabilize resistance, followed by laser trim to adjust the absolute resistance value back to the target specification, thereby resolving the contradiction between resistance stability and absolute resistance accuracy
Solution Approach 2:
The patent applies current trim as a preliminary action before laser trim. By first stabilizing the resistance characteristics through current trim, the subsequent laser trim can focus solely on adjusting the absolute resistance value without worrying about power coefficient variations, making the overall process more effective
2Manufacturing precision
If laser trim is applied to adjust resistance, then absolute resistance is corrected, but resistance stability against power variations is not improved
Solution Approach 1:
The patent reverses the conventional order by applying current trim before laser trim. This preliminary action stabilizes the resistance characteristics and reduces the power coefficient of resistance, ensuring that subsequent laser trimming does not compromise resistance stability while achieving the target absolute resistance value
3Ease of manufacture
If single trimming method is used, then process is simple, but high precision resistance cannot be achieved
Solution Approach 1:
The patent merges current trim and laser trim into a hybrid process that leverages the strengths of both methods. Current trim provides resistance stabilization and power coefficient reduction, while laser trim delivers precise absolute resistance adjustment, together achieving high precision that neither method can achieve alone
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This hybrid approach stabilizes resistor resistance within a precise range, minimizing variations due to power and temperature changes, thereby enhancing the precision and stability of resistors.
Implementation Method 1
applying a first laser trim to a resistor until a resistance of the resistor is higher than a target resistance by a predetermined percentage
Implementation Method 2
The electrical stressing may be achieved by applying a current bias to the resistive material. For example, a SiCr thin film resistor may be heated by an electrical stress as a result of the self/joule heating from applying a current bias to the resistor
Data Source
AI summary
A method for altering a resistance of a resistor including trimming the resistor using a first type of trim approach to increase a resistance measurement of the resistor to above a target resistance value, and iteratively trimming the resistor using a second type of trim approach until a power coefficient of resistance (PCR) or temperature coefficient of resistance (TCR) measurement of the resistor is substantially close to zero.