Molding Compound Structure for Package-on-Package Stress Reduction
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing stress on package-on-package semiconductor devices during fabrication and reliability tests, leading to issues like warpage and fabrication failures, which existing technologies have not adequately addressed.
Innovation Solution
A molding compound layer structure is applied over the package substrate, excluding the corners, which reduces stress by 30% and improves reliability, achieved through the use of a specific deposition technique and dummy blocks to prevent the molding compound from covering these areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the molding compound covers the entire package substrate including corners, then complete coverage and protection is achieved, but stress increases leading to warpage and fabrication failures
Solution Approach 1:
The molding compound coverage is segmented into two regions: a first region covering the central area of the package substrate, and a second region excluding the corner areas. This segmentation allows the molding compound to provide protection where needed while avoiding stress concentration at the corners, thereby reducing warpage and fabrication failures.
Solution Approach 2:
Different regions of the package substrate are treated differently regarding molding compound coverage. The central region receives full coverage for protection, while the corner regions are excluded to prevent stress accumulation. This local differentiation optimizes both reliability and stress management.
2Stability of the object's composition
If the molding compound is deposited to cover corners, then complete encapsulation is achieved, but warpage occurs during subsequent processing
Solution Approach 1:
The encapsulation is segmented such that the molding compound covers the central functional areas while deliberately excluding the corner regions. This segmentation maintains complete encapsulation of critical components while preventing warpage by leaving corners uncovered.
Solution Approach 2:
The molding compound coverage pattern is asymmetric with respect to the package substrate corners, intentionally creating an uneven coverage distribution where corners are excluded. This asymmetric approach prevents the symmetric stress distribution that would otherwise cause warpage.
3Ease of manufacture
If dummy blocks are not used, then the fabrication process is simpler, but the molding compound cannot be prevented from covering corners
Solution Approach 1:
Dummy blocks are placed on the package substrate corners before the molding compound deposition step. This preliminary action prevents the molding compound from covering the corners during deposition, achieving precise coverage control without requiring complex process modifications.
Solution Approach 2:
Dummy blocks serve as intermediary objects that temporarily occupy the corner regions during fabrication. These intermediaries prevent direct contact between the molding compound and corner areas, enabling precise coverage control through a simple and effective mechanism.
Data Source
AI summary
A device includes a package component comprising a substrate and a plurality of bumps formed on the substrate, a semiconductor die on the substrate, a dielectric layer over the substrate, wherein a top surface of the dielectric layer is level with a top surface of the semiconductor die, and a sidewall of the dielectric layer includes a slope portion and a vertical portion and a top package bonded on the package component, wherein the semiconductor die is located between the top package and the substrate.