XRF L-Line Inspection for Accurate Ag/Sn Solder Bump Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional XRF techniques for analyzing Ag/Sn solder bumps in electronic circuits face inaccuracies due to high excitation energies causing penetration into lower layers and interference from atmospheric gases like argon, leading to spectral overlap and reduced accuracy.
Innovation Solution
An XRF inspection system using L-line excitation with inert gas purging to eliminate atmospheric interference, employing nitrogen or helium to create overpressure conditions, reducing the energy requirements and minimizing argon peaks, thereby enhancing the accuracy of Ag/Sn solder bump analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional XRF techniques use high excitation energy (around 50 KeV) for detection of K-line fluorescence, then the detection capability for Ag/Sn bumps is achieved, but the excitation beam penetrates into lower layers and substrate causing interference and reduced accuracy
Solution Approach 1:
The patent changes the excitation energy parameter from conventional high energy (50 KeV for K-line) to lower energy (around 5-10 KeV for L-line) X-ray excitation. This parameter change reduces beam penetration depth, preventing interference from lower layers and substrate, while still enabling effective excitation of L-line fluorescence from Ag and Sn elements in the solder bumps.
Solution Approach 2:
The patent introduces an inert gas atmosphere (nitrogen or helium) as an intermediary medium between the X-ray source and the sample. This intermediary prevents atmospheric gases (particularly argon) from being excited by the X-ray beam, thereby eliminating spectral overlap and interference in the detected fluorescence signal.
2Measurement precision
If conventional XRF inspection is performed in atmospheric conditions, then the inspection process is simple and fast, but atmospheric gases like argon cause spectral overlap and reduce measurement accuracy
Solution Approach 1:
The patent replaces the conventional atmospheric inspection environment with an inert gas atmosphere (nitrogen or helium). This inert environment prevents excitation of atmospheric argon by the X-ray beam, eliminating spectral overlap with the Ag L-line signals and significantly improving spectral resolution and measurement accuracy.
Solution Approach 2:
The patent employs a gas delivery system using pneumatic principles to flow inert gas (nitrogen or helium) through the inspection chamber. This pneumatic system creates a controlled inert atmosphere around the sample, effectively displacing atmospheric gases and preventing their excitation during XRF measurement.
3Measurement precision
If L-line excitation is used with lower energy X-rays, then beam penetration is reduced and accuracy improves, but the excitation efficiency and fluorescence yield may decrease
Solution Approach 1:
The patent optimizes the X-ray excitation energy parameter to match the L-line absorption edges of Ag (around 3.5-4.0 KeV) and Sn (around 2.9-3.3 KeV). By tuning the excitation energy just above these absorption edges, the system achieves efficient fluorescence yield while maintaining shallow penetration depth, thus balancing excitation efficiency with measurement precision.
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 system achieves precise detection of Ag/Sn solder bumps by minimizing interference from atmospheric gases, improving accuracy and reducing spectral overlap, thus ensuring reliable material composition and thickness determination.
Implementation Method 1
The interaction of the X-ray radiation with the elements in the bumps causes fluorescence, emitting secondary X-rays characteristic of the specific elements present in the region of the sample.
Implementation Method 2
An inert gas purging system utilizing nitrogen or helium is employed to eliminate atmospheric gases from the inspection region.
Data Source
AI summary
An XRF inspection system, and a respective method are presented. The system and method are directed at inspection of a sample. The system comprising at least one X-ray radiation source providing X-ray radiation of selected energy spectrum, an optical arrangement for focusing the X-ray radiation onto a selected inspection spot of the sample, and at least one detector configured for detection of radiation emitted from the sample and providing output data indicative of emission spectrum from the sample; wherein the output data comprises data indicative of L-line excitation fluorescent response of the sample.