Reworkable Alpha Particle Barrier for Flip Chip Soft Error Reduction
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Solution Overview
Problem
Electronic devices with flip chip technology are susceptible to soft errors due to alpha particle emissions from substrates and solder, and existing underfill materials make chip rework difficult and costly, especially in multi-chip modules.
Innovation Solution
An easily reworkable alpha particle barrier material, such as high viscosity grade hydrocarbon oils or polymers, is applied between the chip and substrate to block alpha particles and prevent corrosion, allowing for simple chip rework without affecting other dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional epoxy underfill is used to fill the gap between chip and substrate, then alpha particle radiation is absorbed and C4 joint reliability is improved, but chip rework becomes extremely difficult and economically unfeasible
Solution Approach 1:
The patent changes the physical and chemical parameters of the underfill material by using a reversible gel system that transitions from a liquid state during application to a gel state for radiation protection, and can be reversed to liquid state for rework. This parameter change enables the material to provide both protective functions and reworkability that traditional epoxy cannot achieve.
Solution Approach 2:
The underfill system employs dynamic properties by utilizing a gel that can reversibly change its state. The gel can be transformed from a solid-like protective barrier to a liquid-like removable substance through temperature or chemical triggers, enabling the system to adapt between protection mode and rework mode, thus resolving the contradiction between reliability and repairability.
2Ease of repair
If no underfill material is used in the gap, then chip rework is simple and easy, but the device becomes susceptible to soft errors from alpha particle emissions
Solution Approach 1:
The patent applies parameter changes by using a gel material whose physical state can be controlled. In its gel state, the material provides effective alpha particle blocking to reduce soft errors. When rework is needed, the gel can be converted to a liquid state for easy removal. This dynamic parameter control allows the system to achieve both radiation protection and reworkability simultaneously.
Solution Approach 2:
The reversible gel underfill acts as a temporary protective barrier that can be easily removed when needed. Unlike permanent epoxy underfill, this gel material is designed to be transient and reworkable, providing protection during operation but allowing complete removal for chip replacement or upgrades, thus enabling cost-effective rework operations.
3Reliability
If thin film technology is used as alpha particle barrier, then alpha radiation is absorbed, but the device becomes expensive and rework is still difficult
Solution Approach 1:
The patent replaces expensive thin film technology with a cost-effective reversible gel system. The gel material can be applied as a liquid and cures to form the protective barrier, but can be easily removed when needed. This approach significantly reduces manufacturing costs compared to thin film deposition while maintaining alpha particle blocking effectiveness and adding rework capability.
Solution Approach 2:
The patent substitutes complex thin film deposition processes with a simpler liquid gel application method. Instead of requiring vacuum deposition or other complex mechanical processes to apply thin films, the gel can be applied using simple dispensing or coating techniques, greatly simplifying manufacturing and reducing equipment requirements while achieving the same radiation protection function.
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 minimizes soft error rates and allows for easy rework of chips in multi-chip modules by providing a removable alpha particle barrier that also acts as a corrosion barrier, maintaining device reliability and cost-efficiency.
Implementation Method 1
The substrate material and/or the interconnect solder can emit alpha particles. Alpha particle emissions result from the radioactive decay of impurity elements such as polonium, thorium and uranium in the substrate or the interconnect solder. The underfill material also helps to absorb the alpha particle radiation.
Data Source
AI summary
A method and device comprising an easily reworkable alpha particle barrier is provided. The easily reworkable alpha particle barrier is applied in the space between the surface of the chip and the surface of the substrate, and reduces soft error rate (SER). Further, the easily reworkable alpha particle barrier material is chosen from the group of an organic material, a hydrocarbon, more specifically a polyalphaolefin (PAO) oil, and a polymer or filled polymer; wherein the polyalphaolefin oil has a viscosity below 1000 cSt (at 100° C.). The easily reworkable alpha particle barrier material can be used with multichip modules (MCM's) allowing easy device rework of one or more dies without affecting other dies on the same substrate.