Autofocus Interferometric Inspection for Solder Bump Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for detecting solder bump defects on printed circuit board assemblies are slow, inefficient, and often require human intervention, leading to potential rework and increased costs due to the hidden nature of solder bumps, which can crack or delaminate from residual stresses.
Innovation Solution
A high-speed, non-contact, non-destructive autofocus interferometric system using a pulsed infrared laser to generate ultrasound and measure vibrational responses, allowing for the detection of various solder bump defects through signal processing, enabling automated inspection of multiple chip packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional manual inspection methods are used to detect solder bump defects, then detection capability is maintained, but inspection speed and productivity are significantly reduced
Solution Approach 1:
The patent replaces manual visual inspection with an automated optical interferometric system that uses laser light to detect solder bump defects. The system automatically captures images, processes signals, and identifies defects without human intervention, thereby increasing inspection speed and productivity while eliminating the need for manual inspection.
Solution Approach 2:
The system incorporates automated focus adjustment and defect detection algorithms that enable the inspection system to self-regulate and self-evaluate. The autofocus mechanism automatically adjusts the focal plane to capture sharp images of solder bumps, and the signal processing automatically identifies defects, reducing the need for manual operation and increasing throughput.
2Productivity
If solder bumps are hidden from view to achieve high interconnect density, then package size and interconnect capability are improved, but defect detection capability deteriorates
Solution Approach 1:
The patent transitions from two-dimensional visual inspection to three-dimensional interferometric measurement. By using optical interference patterns and adjusting the focal plane through the solder bump layer, the system can detect defects in hidden solder bumps that are not visible from the surface, effectively adding a depth dimension to the detection capability.
Solution Approach 2:
The system uses laser interferometry as an intermediary measurement technique that indirectly detects solder bump defects. The optical interference patterns serve as a mediator that reveals information about the solder bump structure and integrity without requiring direct visual access to the hidden bumps, enabling detection despite their concealed position.
3Ease of manufacture
If residual stresses are present in solder bumps after reflow process, then solder joint formation is achieved, but bump cracking and delamination occur
Solution Approach 1:
The patent performs defect detection immediately after the reflow process while residual stresses are still present. By inspecting solder bumps at this critical stage, the system can identify potential cracking and delamination issues before they propagate, allowing for preventive measures to be taken and improving overall reliability while maintaining the manufacturing process.
Solution Approach 2:
The system provides real-time feedback on solder bump quality by detecting defects caused by residual stresses. This feedback mechanism allows for immediate identification of cracking and delamination issues, enabling process optimization and corrective actions to improve solder bump integrity while maintaining the effectiveness of the reflow process.
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 method provides fast, accurate, and repeatable detection of solder bump defects, reducing rework costs and improving product quality by identifying misalignments, cracks, and other issues without damaging the chip, suitable for online applications.
Implementation Method 1
A pulsed infrared laser is provided and directed onto a surface of an IC chip package. The laser causes rapid heating and cooling of the surface and creates elastic stress waves propagating through the IC chip package.
Implementation Method 2
The laser causes rapid heating and cooling of the surface and creates elastic stress waves propagating through the IC chip package.
Implementation Method 3
A laser vibrometer is positioned to sense and measure out-of-plane displacement of the chip's surface at one or more locations.
Implementation Method 4
an interferometer module disposed to receive reflected laser energy to sense vibrations created with the laser
Data Source
AI summary
High speed autofocus interferometric inspection systems and methods are discussed in this Application. In accordance with some embodiments, an inspection system can generally include a laser module, an interferometer module, and a system controller. The laser can produce laser pulses to excite a device such as a silicon wafer, chip capacitor or chip packaged/silicon die containing a plurality of solder bumps into vibration. The interferometer module can be disposed to receive reflected laser energy from the device to sense vibration displacements created in the device with the laser pulses. The system controller to receive vibration data from the interferometer, the system controller configured to output a control signal for adjusting a relative distance and position between the laser module and the device. Other aspects, features, and embodiments are also claimed and discussed.