Semiconductor Package Rapid Cooling Flatness
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Solution Overview
Problem
Semiconductor packages deform due to thermal expansion mismatches between the semiconductor die and the encapsulation material during gradual cooling, leading to a domed upper surface and non-planar external connection pads, which hinder post-curing processing and solder connections.
Innovation Solution
Rapid cooling of the encapsulation material from curing temperature to less than 50°C within five minutes using fluid flow, such as air blown by fans, to minimize deformation and maintain a flat upper surface and planar base surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gradual cooling is used during post-mold curing, then the encapsulation material is properly cured and stabilized, but the semiconductor package deforms with a domed upper surface and non-planar base surface
Solution Approach 1:
The patent changes the cooling rate parameter from gradual cooling to rapid cooling (cooling from curing temperature to below 50°C within 5 minutes). This parameter change resolves the contradiction by preventing deformation while maintaining curing stability, achieving both a flat upper surface and planar base surface.
2Stress or pressure
If gradual cooling is used during post-mold curing, then the package is maintained under pressure with a clamping device, but the external connection pads become non-planar resulting in poor solder connections
Solution Approach 1:
The patent applies rapid cooling while maintaining clamping pressure, changing the temperature parameter to prevent thermal expansion mismatches. This resolves the contradiction by keeping external connection pads planar for good solder connections while still applying necessary clamping pressure during curing.
3Manufacturing precision
If rapid cooling is applied to prevent deformation, then surface flatness is improved, but cooling time is reduced
Solution Approach 1:
The patent rushes through the cooling phase by applying rapid cooling to reduce temperature from curing temperature to below 50°C within 5 minutes. This skips the prolonged gradual cooling period, achieving surface flatness while minimizing cooling time loss.
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
Prevents deformation and ensures a flat upper surface for easy handling and planar base surface for reliable solder connections, improving the quality of semiconductor packages.
Implementation Method 1
curing of the encapsulation material at a curing temperature
Implementation Method 2
rapidly cooled from the curing temperature to a cooled temperature of less than fifty degrees Centigrade within a period of five minutes or less
Implementation Method 3
differences in coefficients of thermal expansion (CTE) of the semiconductor die and the substrate and the molding compound
Data Source
AI summary
A method for assembling a semiconductor package includes a rapid cooling step after post mold curing of an encapsulation material. The rapid cooling step includes blowing chilled, compressed air over the package for about two minutes. The rapid cooling step does not require any clamping pressure be simultaneously applied to the package. The rapid cooling step reduces a temperature of the encapsulation material from a curing temperature to the cooled temperature within a maximum period of less than five minutes. By using rapid cooling, as opposed to cooling the package under a clamping pressure with ambient air, package warpage due to CTE mismatches is prevented.