Flexible Substrate Package with Openings for Warpage Control
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Solution Overview
Problem
Current flexible packages for portable electronic equipment suffer from substrate shrinkage and warpage issues due to thermal expansion differences between semiconductor dies and flexible substrates, leading to unstable attachments and potential mechanical and electrical failures.
Innovation Solution
A flexible substrate package design featuring a multi-layer structure with insulating and conductive layers, including a first insulating layer, a redistribution layer, and a second insulating layer, along with a structure support to constrain thermal expansion, and an underfill to secure the die, which prevents warpage and enhances attachment stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a flexible substrate is used for semiconductor packaging, then the package size and weight are reduced, but substrate shrinkage and warpage occur due to thermal expansion differences
Solution Approach 1:
The patent modifies the physical parameters of the flexible substrate by incorporating openings that alter its mechanical properties. The openings change the substrate's flexibility and thermal expansion characteristics, allowing it to better accommodate thermal cycling without warpage while maintaining the reduced package size benefit.
Solution Approach 2:
The flexible substrate is segmented by creating openings that divide it into separate regions. This segmentation allows different parts of the substrate to expand and contract independently during thermal cycling, reducing overall warpage and improving attachment stability while preserving the compact package form factor.
2Length of stationary object
If the flexible substrate is made thinner to reduce package height, then the package profile is improved, but the substrate becomes more susceptible to warpage and mechanical failure
Solution Approach 1:
The patent utilizes the flexible substrate as a thin film structure and enhances its performance by adding openings. These openings create a compliant structure that can flex without breaking, maintaining mechanical strength despite the thin profile, while enabling better thermal management and reduced warpage.
Solution Approach 2:
The openings are strategically positioned to create local variations in substrate properties. Areas around the openings have enhanced flexibility and stress distribution characteristics, allowing the thin substrate to maintain overall strength while accommodating thermal expansion differences without warpage.
3Adaptability or versatility
If thermal expansion is allowed to occur freely, then the substrate can accommodate temperature changes, but die attachment becomes unstable due to warpage
Solution Approach 1:
The openings in the flexible substrate act as pre-designed stress relief features that cushion thermal expansion forces before they can cause warpage. This beforehand cushioning allows the substrate to accommodate temperature changes while maintaining die attachment stability, as the openings absorb expansion stresses in advance.
Solution Approach 2:
The openings serve as intermediary elements between the die and the rest of the substrate structure. They mediate the thermal expansion forces, allowing the substrate to adapt to temperature changes while the openings absorb and distribute stresses, preventing direct transmission of warpage forces to the die attachment.
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 solution effectively reduces substrate shrinkage and warpage, ensuring stable die attachments and preventing electrical and mechanical failures by managing thermal stresses through a controlled expansion coefficient and structural support, thus enhancing the reliability of semiconductor packages.
Implementation Method 1
substrate shrinkage and warpage issues due to thermal expansion differences between semiconductor dies and flexible substrates
Implementation Method 2
an underfill to secure the die
Data Source
AI summary
Methods and apparatus are disclosed for forming ultra-thin packages for semiconductor devices on flexible substrates. A flexible substrate may comprise a plurality of insulating layers and redistribution layers. Openings of the flexible substrate may be formed at one side of the flexible substrate, two sides of the flexible substrate, or simply cut through the flexible substrate to divide the flexible substrate into two parts. Connectors may be placed within the opening of the flexible substrate and connected to redistribution layers of the flexible substrate. Dies can be attached to the connectors and electrically connected to the connectors and to the redistribution layers of the flexible substrate. Structure supports may be placed at another side of the flexible substrate on the surface or within an opening.