Selective Molding for ICs Using Polyimide Containment
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Solution Overview
Problem
Glob top material bleed out and outgassing during the cure process in packaged electronic devices lead to delamination and bond wire integrity issues, increasing production costs and complexity.
Innovation Solution
A dual package structure with a stress absorbing material, such as epoxy, is used to encapsulate the semiconductor dies and bond wires, and a polyimide layer is applied to prevent lateral bleed out, combined with controlled deposition and curing processes to mitigate material movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glob top material is applied to cover and protect semiconductor dies, then protection against contamination and mechanical stress is improved, but material bleed out during cure process causes delamination and bond wire integrity issues
Solution Approach 1:
A boundary material layer (such as polyimide) is deposited on the die surface before applying the glob top material. This preliminary action creates a containment structure that prevents material bleed out during the cure process, allowing the glob top to be applied without causing delamination or bond wire integrity issues.
Solution Approach 2:
The boundary material layer acts as an intermediary between the glob top material and the die surface. It provides a controlled interface that contains the glob top material within the desired area, preventing direct contact and potential damage to the bond wires and stitches while still allowing the glob top to provide its protective function.
2Manufacturing precision
If boundary material layer is formed on die surface to prevent glob top bleed out, then material containment is improved, but controlled deposition within boundary layer becomes difficult
Solution Approach 1:
The boundary material layer is deposited first to establish containment boundaries before the glob top material is applied. This preliminary structuring simplifies the subsequent deposition process by providing clear physical boundaries that guide material placement, making the overall manufacturing process easier to control.
Solution Approach 2:
The boundary material layer creates zones of different properties: the boundary region provides containment while the central region allows for proper glob top deposition. This local differentiation of material properties and functions enables controlled deposition within the boundary layer while maintaining ease of manufacture.
3Manufacturing precision
If multiple concentric rings are formed to prevent bleed out, then material containment is improved, but production cost and complexity increase
Solution Approach 1:
A single boundary material layer is deposited as a preliminary containment structure before glob top application. This single-layer approach provides sufficient containment without requiring multiple concentric rings, thereby reducing production cost and structural complexity while maintaining effective material containment.
4Manufacturing precision
If processing time for deposition and curing is precisely controlled to mitigate bleed out, then material containment is improved, but production cost and time increase
Solution Approach 1:
The boundary material layer is deposited in advance to establish containment boundaries before glob top material application. This preliminary structure prevents material bleed out during standard curing processes, eliminating the need for precisely controlled and extended processing times, thereby reducing production cycle time and cost.
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 delamination and enhances bond wire integrity by structurally isolating the internal dies from mechanical stress and preventing glob top material bleed out, thereby improving the reliability of packaged electronic devices.
Implementation Method 1
The stress absorbing structure, such as an epoxy material, extends on the second semiconductor die and on a portion of the second side of the first semiconductor die
Implementation Method 2
A boundary material layer, such as a ring of polyimide can be formed on the die surface to mitigate glob top bleed out
Data Source
AI summary
A method includes performing a first molding process to enclose a portion of a first semiconductor die in a first package structure with an opening that exposes a portion of a second semiconductor die mounted to the first semiconductor die, as well as performing a deposition process to deposit a stress absorbing material in the opening of the first package structure to cover the portion of the second semiconductor die, and performing a second molding process to enclose a portion of the stress absorbing structure in a second package structure that extends on a side of the first package structure.