Solder Joint Electromigration Measurement with Four-Terminal Daisy Chains
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Solution Overview
Problem
Existing methods for solder joint resistance measurement using two-terminal measurement cannot accurately determine the resistance of individual solder joints, limiting effective reliability evaluation of solder joint electromigration.
Innovation Solution
A method and apparatus utilizing a daisy chain structure with voltage test pads at both ends of each solder joint, enabling four-terminal measurement to determine the resistance of individual solder joints by measuring voltage differences across selected subchains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-terminal measurement is used to measure solder joint resistance, then the measurement process is simple, but only total resistance of the whole daisy chain can be measured rather than resistance of a single solder joint
Solution Approach 1:
The patent divides the daisy chain into multiple measurable segments by introducing voltage test pads at both ends of each solder joint. This segmentation enables the measurement system to isolate and measure the resistance of individual solder joints or subchains rather than only the total chain resistance, thereby achieving precise single joint resistance measurement while maintaining a relatively simple test structure.
Solution Approach 2:
The patent introduces voltage test pads as intermediary elements that facilitate four-terminal measurement. These test pads serve as mediators between the measurement instrument and the solder joints, enabling precise voltage measurement across individual joints without directly contacting the solder joint itself, thus achieving high measurement precision while keeping the overall structure simple.
2Measurement precision
If a daisy chain of certain length is desired to meet resistance measurement precision requirement, then measurement precision is improved, but the traditional daisy chain has merely two ends limiting single joint measurement
Solution Approach 1:
By segmenting the daisy chain with voltage test pads at each solder joint, the patent enables flexible measurement of any subchain length. Users can measure individual joints, pairs of joints, or any combination of joints by selecting appropriate voltage test pad pairs, providing both high measurement precision and great measurement flexibility without being constrained to fixed chain lengths.
Solution Approach 2:
The voltage test pads provide multi-functionality by serving as both measurement points for individual joints and as connection points for measuring various subchain combinations. This universal design allows the same test structure to accommodate different measurement requirements (single joint, multiple joints, different chain lengths) without requiring separate test fixtures, thereby enhancing both precision and adaptability.
3Measurement precision
If four-terminal measurement is implemented to measure individual solder joint resistance, then single joint resistance measurement is enabled, but test structure complexity increases
Solution Approach 1:
The patent extracts the voltage measurement function from the current path by introducing separate voltage test pads that are electrically connected in parallel with each solder joint. This extraction allows the voltage measurement circuit to operate independently from the current injection circuit, enabling true four-terminal measurement where voltage sensing does not affect current flow, thereby achieving single joint resistance measurement with minimal additional structural complexity.
Solution Approach 2:
By placing voltage test pads at both ends of each solder joint, the patent creates equipotential measurement points that accurately represent the voltage drop across the joint. This equipotential arrangement ensures that voltage measurement is performed without introducing additional contact resistance or measurement errors, achieving precise single joint resistance measurement while keeping the test structure simple through direct parallel connection.
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
Enables precise measurement of individual solder joint resistance, enhancing reliability evaluation of solder joint electromigration and reducing test costs by eliminating parasitic resistances.
Implementation Method 1
the controller is configured to determine, according to the voltage, a resistance of the one or more solder joints
Data Source
AI summary
Disclosed are a method and an apparatus for measuring electromigration of solder joints. The method includes: determining, according to voltage test pads led out from both ends of one or more solder joints, a voltage of a daisy subchain between the one or more solder joints (S502); and determining, according to the voltage, a resistance of the one or more solder joints (S504).