Solder Void Evaluation Using Center-Weighted Pixel Analysis
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Solution Overview
Problem
Current methods for evaluating voids in solder balls rely solely on the number and area ratio of voids, which are insufficient for determining reliability, and are time-consuming, especially when dealing with large numbers of solder balls.
Innovation Solution
A void evaluation apparatus and method that calculates a solder evaluation function using pixel values and a weight function that maximizes at the solder center, allowing for rapid and precise assessment of void influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional void evaluation methods using only number and area ratio are used, then evaluation simplicity is maintained, but evaluation precision is insufficient
Solution Approach 1:
The patent applies local quality by introducing a weight function that assigns different weights to different regions within the solder ball. The weight function w(ri) = (r0 - ri) / r0 gives higher weights to voids closer to the center (ri接近0) and lower weights to voids near the edge (ri接近r0). This resolves the contradiction by making the evaluation more precise through location-aware weighting without requiring complex additional hardware, only a computational algorithm.
2Measurement precision
If detailed void analysis is performed for all solder balls, then evaluation precision improves, but evaluation time increases
Solution Approach 1:
The patent changes the evaluation parameter from simple counting to a weighted sum calculation. Instead of merely counting voids or measuring their area ratios, the system calculates Σ(w(ri) × pi) where pi is the pixel value indicating void presence and w(ri) is the weight based on radial distance. This parameter transformation enables more precise evaluation while maintaining computational efficiency suitable for high-speed processing of multiple solder balls.
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 high-speed and accurate evaluation of voids in solder balls, improving connection reliability and reducing evaluation time.
Implementation Method 1
Japanese Laid-open Patent Application Publication No. 2006-226875 discloses a method of detecting a bonding defect of a solder ball by X-ray
Data Source
AI summary
A void evaluation apparatus in a solder includes an evaluation function calculation unit for calculating a solder evaluation function by using a pixel value pi contained in the voids that is set to 1 and the pixel value pi not contained in the voids is 0 for each pixel constituting an image in the solder, and by using a weight function w(ri), which is maximum at a solder center (ri=0), and is 0 at a maximum radius (ri=r0) for a distance ri from the solder center. The apparatus further has a void evaluation unit for evaluating that the influence of voids is larger as the evaluation function is relatively larger for the each solder.∑i=1Nw(ri)pi∑i=1Nw(ri)×100i: pixel number (1−N)pi: pixel value (0 or 1)w(ri): weighting function