Underfill Dispensing Based on Chip Standoff Height Variation
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Solution Overview
Problem
The use of low temperature soldering processes in semiconductor device packaging leads to variations in standoff height, resulting in insufficient underfill material coverage and the formation of voids or gaps, which compromises the reliability of solder joints.
Innovation Solution
A method and system for calculating the standoff height between a substrate and semiconductor chips using image capture, 3D x-ray, laser height sensing, or 3D automated optical inspection devices to determine the volume of underfill material needed, ensuring accurate dispensing to fill the space between the substrate and chips, even with varying standoff heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low temperature soldering processes are used, then energy consumption is reduced and carbon footprint is decreased, but standoff height variations increase leading to insufficient underfill coverage
Solution Approach 1:
The system performs preliminary measurement of standoff height using optical sensors or laser displacement sensors before underfill dispensing. This allows the dispensing parameters to be adjusted in advance based on the actual measured height, ensuring complete coverage even when standoff height varies due to low temperature soldering processes
Solution Approach 2:
The system implements feedback control by measuring the actual standoff height of each semiconductor chip and using this information to adjust the underfill dispensing volume and pressure. The controller modifies dispensing parameters in real-time based on measured variations, ensuring consistent coverage across all chips regardless of soldering process variations
2Loss of energy
If low temperature soldering processes are used, then energy consumption is reduced, but voids or gaps form in the underfill material
Solution Approach 1:
The system measures standoff height before dispensing to calculate the precise volume of underfill material needed. This preliminary measurement ensures that sufficient material is dispensed to completely fill the space between chip and substrate, preventing void formation that would otherwise occur with fixed-volume dispensing
Solution Approach 2:
The system dynamically changes dispensing parameters including volume, pressure, and speed based on measured standoff height. When higher void risk is detected, the system increases dispensing volume and adjusts pressure to ensure complete space filling, eliminating the harmful effect of voids while maintaining energy efficiency
3Device complexity
If fixed volume underfill dispensing is used, then dispensing process is simple, but coverage is insufficient when standoff height varies
Solution Approach 1:
The system uses feedback control where optical sensors or laser sensors measure the actual standoff height of each chip, and the controller adjusts dispensing volume and pressure accordingly. This closed-loop control ensures precise coverage for each chip while maintaining an automated process that is relatively simple to implement
Solution Approach 2:
The system performs self-adjustment by automatically measuring standoff height and calculating required dispensing parameters without manual intervention. The automated measurement and adjustment process maintains manufacturing precision while keeping the overall system complexity manageable through integration
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
Ensures complete and reliable coverage of the space between the substrate and semiconductor chips, reducing the risk of voids and gaps, and enhancing the reliability of solder joints by accurately determining and dispensing the required volume of underfill material.
Implementation Method 1
calculating the at least one standoff height based on laser height sensing
Implementation Method 2
calculating the at least one standoff height based on a 3-dimensional x-ray of the substrate and the at least one semiconductor chip electrically connected thereto
Data Source
AI summary
A method of dispensing an underfill material on a semiconductor device package. A substrate having a semiconductor chip electrically connected thereto and offset from the substrate by solder joints is provided. The semiconductor chip has a footprint defined by a length and width of the semiconductor chip. Standoff heights between the substrate and the semiconductor chip are calculated and used to determine a volume of underfill material needed to substantially fill a space between the substrate and the semiconductor chip. The determined volume of underfill material is dispensed on the substrate such that the space between the substrate and the semiconductor chip is substantially filled by the underfill material. The method may allow for improved dispensing an underfill material to substantially fill the space between the substrate and semiconductor chip when variations in standoff height are present.