Semiconductor Package Warpage Control via Segmented Curing
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Solution Overview
Problem
Semiconductor packages experience warpage due to thermal expansion differences between printed circuit boards (PCBs) and encapsulants, which worsens with thinner PCBs and encapsulants, affecting the sawing process during package assembly.
Innovation Solution
A method involving disposing semiconductor chips on a package substrate with sawing lines, forming an encapsulant, performing a first curing, cutting grooves along the sawing lines, and then dividing the package assembly into units by cutting the substrate or encapsulant, with a second curing step to minimize warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of PCB and encapsulant are reduced to achieve smaller package size, then the compactness and integration are improved, but the warpage occurrence is increased due to thermal expansion differences
Solution Approach 1:
The patent divides the package assembly into multiple sections by forming grooves along the sawing lines before final cutting. This segmentation allows the encapsulant to be divided into separate regions that can independently accommodate thermal expansion stresses, preventing warpage while maintaining thin dimensions. The grooves create discrete segments that reduce the cumulative effect of thermal mismatch across the entire package.
Solution Approach 2:
The patent performs the first curing of the encapsulant before forming the grooves and subsequent cutting. This preliminary curing establishes the basic structural integrity and reduces initial warpage. By completing the curing process in stages (first curing before groove formation, second curing after groove formation), the patent allows the encapsulant to set in a controlled manner that minimizes thermal expansion-induced distortion in the final thin package structure.
2Reliability
If heat is applied during the fabrication process to achieve proper curing, then the encapsulation quality is improved, but warpage appears due to thermal expansion differences between PCB and encapsulant
Solution Approach 1:
The patent segments the encapsulant by forming grooves along the sawing lines to divide it into multiple independent regions. This segmentation allows each segment to expand and contract independently during heating, reducing the cumulative thermal stress that causes warpage. The grooves act as stress relief features that maintain encapsulation quality while preventing distortion during the curing process.
Solution Approach 2:
The patent performs a first curing of the encapsulant before forming the grooves and subsequent cutting operations. This preliminary curing establishes the foundational encapsulation quality and structural integrity. By completing additional curing after groove formation (second curing), the patent ensures that the encapsulant achieves full curing properties while the segmented structure already in place prevents warpage during the thermal process.
3Productivity
If the package assembly is divided into unit packages by cutting along sawing lines, then the manufacturing efficiency is improved, but the warpage control becomes more difficult
Solution Approach 1:
The patent forms grooves along the sawing lines to pre-segment the encapsulant before the final cutting operation. This pre-segmentation ensures that when the package assembly is divided into unit packages, each unit has already been separated into manageable segments by the grooves, making the cutting process easier and more precise. The grooves guide the cutting operation and ensure clean separation while maintaining alignment, thus improving both efficiency and precision.
Solution Approach 2:
The patent performs the first curing of the encapsulant before forming the grooves and subsequent cutting. This preliminary curing stabilizes the package assembly structure, making it more rigid and easier to handle during the groove formation and cutting operations. By completing the curing process in stages, the patent ensures that the material is sufficiently stable to maintain its shape and alignment during the division process, improving manufacturing precision while maintaining efficiency.
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 method reduces warpage in the package assembly and final unit semiconductor packages, improving the fabrication process by controlling the curing and cutting processes to align the encapsulant and substrate surfaces effectively.
Implementation Method 1
forming a package assembly by performing a first curing of the encapsulant
Data Source
AI summary
The method includes disposing semiconductor chips on a package substrate having sawing lines, forming an encapsulant to cover the semiconductor chips on the package substrate, forming a package assembly by a first curing of the encapsulant, forming first grooves by cutting the encapsulant along the sawing lines, performing a second curing of the encapsulant, and dividing the package assembly into unit semiconductor packages by cutting the package substrate along the sawing lines and forming second grooves to overlap the first grooves.