IC Packaging Stress Buffer Sheet Mitigates Thermal Expansion Mismatch
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Solution Overview
Problem
The mismatch of coefficients of thermal expansion between chip materials and substrates in conventional wire bonding BGA product structures leads to thermal stress, degrading the performance of integrated circuit packaging products.
Innovation Solution
An IC packaging structure and method that incorporates a stress buffer sheet with a mesh and spring structure, mounted on a substrate with a groove, to buffer thermal stress acting on the packaged chip, preventing direct contact and thus mitigating performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a face-up chip is directly connected to the substrate through wire bonding, then the packaging dimension is reduced and I/O pin count is increased, but thermal stress degrades the performance of the packaged chip
Solution Approach 1:
A stress buffer sheet is introduced as an intermediary layer between the substrate and the packaged chip. This buffer sheet absorbs and distributes the thermal stress generated by coefficient of thermal expansion mismatch, preventing direct transmission of stress to the chip while maintaining the compact packaging structure.
Solution Approach 2:
The stress buffer sheet is strategically positioned only in the region where thermal stress concentration occurs between the substrate and packaged chip. This localized intervention provides stress relief exactly where needed without adding unnecessary complexity or volume to the overall packaging structure.
2Adaptability or versatility
If material layers with different thermal expansion coefficients are stacked together, then integration level is improved, but stress accumulation causes degradation and invalidation of product performance
Solution Approach 1:
The stress buffer sheet converts the harmful thermal stress into a manageable form by absorbing and distributing it across its structure. The buffer sheet's material properties allow it to accommodate differential thermal expansion between layers, transforming the potentially damaging stress into a controlled mechanical deformation that does not compromise chip performance.
Solution Approach 2:
The stress buffer sheet is constructed from composite materials that combine the advantages of different substances - providing both mechanical support and stress absorption capabilities. This composite structure enables the buffer sheet to handle the complex thermal-mechanical interactions between layers with different expansion coefficients.
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
Effectively buffers thermal stress caused by coefficient mismatch, enhancing the reliability and performance of integrated circuit packaging by absorbing thermal expansion and contraction deformations, thereby protecting the packaged chip.
Implementation Method 1
the stress buffer sheet is used for buffering stress acting on the packaged chip
Implementation Method 2
a stress caused by mismatch of coefficients of thermal expansion of a chip material silicon (the coefficient of thermal expansion is 2.5 ppm/C) with the substrate material (the coefficient of thermal expansion is 12 ppm/C)
Data Source
AI summary
Embodiments of the present disclosure provide an IC packaging structure and an IC packaging method, relating to the chip packaging field. The IC packaging structure includes: a substrate, a stress buffer sheet mounted on the substrate; a packaged chip mounted on the stress buffer sheet, and a plastic package body coated outside the packaged chip, wherein the packaged chip is electrically connected to the substrate, and the stress buffer sheet is used for buffering stress acting on the packaged chip. Compared with the prior art, in the IC packaging structure provided in the present disclosure, the stress buffer sheet is mounted on the substrate through silver glue, the packaged chip is mounted on the stress buffer sheet through silver glue.