Package-in-Package Internal Stiffener for Thermal Warping
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Solution Overview
Problem
The Package-in-Package (PiP) system faces yield loss due to warping of internal stacking modules during thermal cycles, stress concentrations at semiconductor die corners, and interconnect failures, which existing technologies have not adequately addressed.
Innovation Solution
A package-in-package system is designed with an internal stiffening module comprising a rigid substrate and thermal interface material, providing mechanical rigidity and stress relief by attaching a top internal stacking module upside-down on the internal stiffening module, which includes a die receptacle and thermal interface material to mitigate thermal stress and facilitate self-alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Package-in-Package (PiP) approach is used to mount multiple semiconductor dies on a package substrate, then integration density and modularity are improved, but warping of internal stacking modules during thermal cycles causes yield loss
Solution Approach 1:
The patent divides the package structure into separate internal stacking modules (ISM) that can be assembled in a modular fashion. Each ISM is a self-contained unit with its own semiconductor die and package substrate, allowing independent fabrication and testing before final assembly. This segmentation enables the complex multi-chip package to be built from smaller, more manageable units, improving both integration density and yield by isolating potential failure points.
Solution Approach 2:
The patent introduces an underfill material as an intermediary substance between the semiconductor die and package substrate. This underfill material serves as a stress-relief layer that compensates for coefficient of thermal expansion (CTE) mismatches between different materials during thermal cycling. By placing this intermediary layer, the patent prevents warping and delamination while maintaining the modular PiP structure.
2Reliability
If internal stacking modules are assembled through thermal cycles, then interconnect bonding is improved, but stress concentrations at semiconductor die corners induce chip failures
Solution Approach 1:
The patent applies underfill material beforehand during the assembly process, before thermal cycling occurs. This underfill material acts as a pre-positioned cushioning layer that distributes mechanical stress uniformly across the semiconductor die and package substrate interface. By providing this stress distribution mechanism in advance, the patent prevents stress concentrations at vulnerable locations such as die corners during subsequent thermal cycling and interconnect bonding processes.
3Adaptability or versatility
If package asymmetries (geometry and materials) are present in PiP structure, then design flexibility is improved, but cooling and heating cycles induce bending of internal stacking modules
Solution Approach 1:
The patent carefully selects and matches the coefficient of thermal expansion (CTE) parameters of the materials used in the internal stacking modules. By controlling and matching these thermal parameters across different materials (semiconductor die, package substrate, underfill), the patent minimizes differential expansion and contraction during thermal cycling. This parameter matching allows design flexibility in the PiP structure while preventing warping and bending that would otherwise result from package asymmetries.
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
This configuration significantly reduces yield loss by minimizing thermal stress-induced delamination and cracking, enabling higher interconnect density and cost-effective manufacturing of multi-chip packages with improved reliability.
Implementation Method 1
Cooling and heating cycles encountered in the package fabrication process can induce bending of internal stacking modules due to package asymmetries (both geometry and materials asymmetries)
Data Source
AI summary
The present invention is a method of manufacture of a package-in-package system, comprising: providing a bottom internal stacking module incorporating a semiconductor die and a package substrate, attaching an internal stiffening module, with a die receptacle, on the bottom internal stacking module, and attaching a top internal stacking module incorporating a further semiconductor die and a further package substrate upside-down on the internal stiffening module.