PCB Test Coupon for Thermal Fracture Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing PCB test coupons using daisy chain patterns are limited in detecting the initiation point of fracturing or cracking in plated holes/vias during thermal cycling, as they require multiple plated holes/vias and can only detect fractures or cracks at an advanced stage, making it difficult to obtain statistically significant data.
Innovation Solution
A PCB test coupon with a matrix of plated holes/vias and trace patterns that allows for individual resistance measurement of each plated hole/via using a limited set of test channels, enabling earlier detection of fractures or cracks and increasing the amount of electrical resistance test data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If daisy chain test nets with multiple plated holes/vias are used, then the amount of electrical resistance test data increases, but the ability to detect the initiation point of fractures or cracks is limited
Solution Approach 1:
The patent divides the test net into multiple independent single-hole test nets instead of using a daisy chain configuration. Each plated hole or via is tested individually through separate test nets, allowing precise identification of which specific hole or via has fractured or cracked. This segmentation enables both individual detection precision and aggregated statistical data collection.
2Measurement precision
If a single plated hole/via is tested individually, then the detection precision of fracture initiation point is improved, but the amount of electrical resistance test data decreases
Solution Approach 1:
The patent creates multiple test nets that each serve the dual function of individual hole testing and collective statistical analysis. Each test net is designed to test a single plated hole or via independently, while the entire array of test nets collectively provides statistically significant data. This multi-functionality resolves the contradiction between individual precision and aggregate data quantity.
Solution Approach 2:
The patent transitions from a single-dimensional daisy chain test net to a multi-dimensional array of independent test nets. By organizing multiple single-hole test nets in a systematic arrangement, the patent enables simultaneous individual measurement precision and collective statistical power, adding the dimension of parallel testing capability.
3Device complexity
If daisy chain test nets are used, then the device complexity is reduced, but the reliability of detecting early-stage fractures or cracks decreases
Solution Approach 1:
The patent segments the test configuration into multiple independent single-hole test nets, each capable of independently detecting fractures or cracks at their specific location. This segmentation improves reliability by eliminating the masking effect in daisy chains where a single fracture might be obscured by the presence of other holes, while the systematic arrangement maintains manageable device complexity.
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
The solution enables earlier detection of fractures or cracks in plated holes/vias and increases the amount of electrical resistance test data available, improving the reliability of thermal exposure testing.
Implementation Method 1
Electrical resistance of the daisy chain test net of plated holes/vias was then measured using a 4-wire kelvin bridge measurement system
Implementation Method 2
thermal cycling environment that sequentially exposes them to hot and cold temperature extremes in cycles causing expansion and contraction of the plated hole/via with each thermal cycle
Data Source
AI summary
A printed circuit board (PCB) test coupon for thermal exposure and electrical testing includes a double sided or multi-layer substrate with a plurality of vias formed within the substrate of the test coupon (blind, buried, stacked vias) or extending through the entire substrate (through hole/via) from a first surface on the first side of the plated hole/via to a second surface on the second side of the plated hole/via. Each of a first plurality of trace patterns interconnect a subset of the plurality of plated holes/vias on the first side of the plated holes/vias, and each of a second plurality of trace patterns interconnect a different subset of the plurality of plated holes/vias on the second side of the plated holes/vias. The first and second pluralities of trace patterns have different patterns and connect to connection points in a connector pattern defined in the substrate. One of the second plurality of trace patterns is configured to measure temperature and two of the second plurality of trace patterns are configured to measure calibration/drift by resistance measurements. The test coupon provides test nets that include a single plated hole/via, and optionally includes daisy chain test nets. A resistance measurement of each plated hole/via (or daisy chain) is provided by connecting 2 wires of a 4-wire kelvin bridge measurement system to the first and second sides of the plated hole/via (or daisy chain) using connection points for one of the first plurality of trace patterns and one of the second plurality of trace patterns that connect to each side of the said plated hole/via (or daisy chain).