Sheet-shaped prepreg for low thermal expansion packaging
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Solution Overview
Problem
Fan-out wafer-level packaging (FOWLP) experiences warpage due to the high coefficient of linear thermal expansion of encapsulating resins, leading to cracking and reduced flexibility, which existing solutions attempt to address by adding fillers but result in increased melt viscosity and brittleness.
Innovation Solution
A sheet-like prepreg comprising a porous support with a low coefficient of linear thermal expansion, impregnated with a curable composition containing an epoxide with a specific weight per epoxy equivalent, providing a cured product with low thermal shrinkage and expansion, thus offering excellent anti-warpage and cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large amount of filler is added to lower the coefficient of linear thermal expansion of encapsulating resin, then the coefficient of linear thermal expansion is reduced, but the melt viscosity increases significantly and the resin becomes stiff and brittle
Solution Approach 1:
The invention changes the chemical composition parameters of the curable composition by specifying epoxides with particular weight per epoxy equivalent ranges (140-3000 g/eq) and restricting certain compound types. This parameter optimization allows achieving low thermal expansion (≤10 ppm/K) without requiring excessive filler addition, thereby avoiding the viscosity and brittleness problems associated with high filler content.
Solution Approach 2:
The invention creates a composite system combining a porous support (made from materials with low thermal expansion such as glass fibers or metal foils) with a specifically formulated curable composition. This composite structure achieves low overall thermal expansion through the support material while the optimized curable composition maintains appropriate flexibility and processability without excessive filler loading.
2Stability of the object's composition
If a large amount of filler is added to lower the coefficient of linear thermal expansion of encapsulating resin, then the coefficient of linear thermal expansion is reduced, but the resin becomes stiff and brittle with lower flexibility
Solution Approach 1:
The invention optimizes the molecular weight parameters of the epoxide components (140-3000 g/eq weight per epoxy equivalent) to achieve the right balance between thermal expansion properties and mechanical flexibility. This parameter control allows the cured product to maintain appropriate flexibility (glass transition temperature from -60°C to 100°C) while achieving low thermal expansion, avoiding the brittleness caused by high filler content.
Solution Approach 2:
The porous support structure (made from low thermal expansion materials) combined with the optimized curable composition creates a composite that achieves low thermal expansion without relying on excessive filler addition. The support provides structural integrity and low thermal expansion, while the carefully formulated curable composition maintains flexibility and prevents brittleness.
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 sheet-like prepreg achieves appropriate flexibility and resistance to warpage and cracking, making it suitable for FOWLP and substrate warpage prevention with reduced thermal expansion and shrinkage.
Implementation Method 1
a sheet-like prepreg that includes a sheet-like porous support and a curable composition... The sheet-like porous support is impregnated with the curable composition... The sheet-like prepreg gives a cured product that has a thermal shrinkage percentage and a thermal expansion coefficient at low levels
Data Source
AI summary
Provided is a sheet-like prepreg that has both a low coefficient of linear thermal expansion and high flexibility and offers excellent anti-warpage performance and cracking resistance. The sheet-like prepreg according to the present invention includes a curable composition and a sheet-like porous support impregnated with the curable composition. The sheet-like porous support is made from a material having a coefficient of linear thermal expansion of 10 ppm/K or less. The sheet-like prepreg gives a cured product having a glass transition temperature of −60° C. to 100° C. The curable composition includes one or more curable compounds (A) and at least one of a curing agent (B) and a curing catalyst (C). The curable compounds (A) include an epoxide having a weight per epoxy equivalent of 140 to 3000 g/eq in an amount of 50 weight percent or more of the totality of the curable compounds (A).