Stiffener Ring Assembly for FC-BGA Substrate Warpage Control
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Solution Overview
Problem
In FC-BGA packaging, the difference in coefficients of thermal expansion between various materials leads to warpage deformation of the substrate during high-temperature reflow soldering, resulting in failures such as bridging and head-in-pillow effects of the solder ball.
Innovation Solution
A stiffener ring with an annular body and an adjustment block is used to correct warpage of the substrate. The adjustment block has a lower coefficient of thermal expansion than the stiffener ring body, and is fastened to at least one corner of the stiffener ring body. This configuration alleviates the 'M-shape' overpressure phenomenon of warpage deformation and improves the flatness of the surface packaging assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a stiffener ring is used to reduce substrate warpage, then substrate flatness is improved, but M-shape overpressure phenomenon occurs at high temperature
Solution Approach 1:
The patent applies local quality by attaching adjustment blocks with different thermal expansion coefficients to specific corners of the stiffener ring. This creates localized regions with different mechanical properties to counteract the M-shape overpressure phenomenon while maintaining overall substrate flatness support.
Solution Approach 2:
The patent uses composite materials by combining the stiffener ring body with adjustment blocks made of different materials having different coefficients of thermal expansion. This composite structure allows the stiffener ring to provide mechanical support while the adjustment blocks compensate for thermal warpage effects.
2Stability of the object's composition
If stiffener ring provides mechanical support, then substrate stability is improved, but thermal expansion difference causes warpage deformation
Solution Approach 1:
The patent applies parameter changes by selecting materials for the adjustment blocks with specific coefficients of thermal expansion that are lower than the stiffener ring body material. This parameter difference allows the adjustment blocks to compensate for thermal expansion effects while the stiffener ring provides mechanical support, maintaining substrate stability without warpage deformation.
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 stiffener ring effectively reduces warpage of the substrate and improves the flatness of the surface packaging assembly, thereby reducing the probability of solder ball failures and enhancing the reliability of the packaging.
Implementation Method 1
A coefficient of thermal expansion of the adjustment block is less than a coefficient of thermal expansion of the stiffener ring body: Coordination between the adjustment block and the stiffener ring body alleviates an 'M-shape' overpressure phenomenon of a warpage deformation caused by the stiffener ring to the substrate at a high temperature
Data Source
AI summary
This application provides a stiffener ring and a surface packaging assembly. The stiffener ring is configured to correct warpage of a substrate of the surface packaging assembly. The stiffener ring includes an annular stiffener ring body and an adjustment block that is disposed at a same layer as the stiffener ring body and that is fastened to at least one corner of the stiffener ring body. A coefficient of thermal expansion of the adjustment block is less than a coefficient of thermal expansion of the stiffener ring body. Coordination between the adjustment block and the stiffener ring body alleviates an “M-shape” overpressure phenomenon of a warpage deformation caused by the stiffener ring to the substrate at a high temperature, reduces warpage of the substrate, and improves flatness of the surface packaging assembly.