Cap-Type Die Seal Design for Thermal Stress Reduction
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Solution Overview
Problem
Conventional die seals fail to effectively reduce thermal stress-induced cracking in semiconductor dies during encapsulation, leading to reduced yields and increased production costs due to the mismatch in thermal expansion coefficients between the semiconductor die and the mold material.
Innovation Solution
A 'cap-type' die seal design that covers the top surface and side faces of the semiconductor die, with a unique structure allowing the mold material connection to increase gradually from the middle to the corners, reducing stress by controlling the contact area and location, and a curved die seal design that produces a wider groove geometry to alleviate manufacturing difficulties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional die seal is used during encapsulation, then the die surface is protected from mold material contact, but thermal stress-induced cracking occurs due to mismatch in thermal expansion coefficients
Solution Approach 1:
The die seal incorporates protrusions that create localized contact points with the mold material, concentrating the interaction at specific regions rather than uniform contact. This localizes the stress distribution and allows different regions of the die seal to have different functional characteristics, reducing overall thermal stress on the die.
Solution Approach 2:
The die seal features a curved lower surface instead of a flat surface, creating a rounded geometry that distributes contact forces more evenly across the die surface. This curvature reduces stress concentration points and allows for more uniform stress distribution during thermal expansion and contraction cycles.
2Reliability
If the die seal extends beyond the die edge to prevent mold material leakage, then sealing effectiveness improves, but undercut is created in the mold material
Solution Approach 1:
The die seal extends slightly beyond the die edge in specific regions (creating controlled overhang) but includes protrusions that prevent excessive extension. This partial extension provides adequate sealing while the protrusions limit the overhang to prevent severe undercut formation in the mold material.
Solution Approach 2:
The die seal geometry includes variable parameters such as protrusion height, curvature radius, and extension distance that can be adjusted to optimize the balance between sealing effectiveness and undercut prevention. By changing these geometric parameters, the seal performance and mold material geometry can be simultaneously optimized.
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 'cap-type' die seal reduces thermal stresses by approximately 60% with no change in warpage, while the curved die seal design enhances manufacturability and reliability by creating a more robust groove geometry, minimizing die cracking and improving yield.
Implementation Method 1
a deformable die seal design that, when pressed upon the semiconductor die, prevents leakage of mold material onto an upper surface of the semiconductor die
Data Source
AI summary
Novel die seals control contact of a mold material with the surfaces of a semiconductor die during encapsulation, reducing stresses due to a mismatch of the coefficient of thermal expansion of the encapsulant and the semiconductor die, thereby reducing cracking of the semiconductor die, resulting in increased yields and lower costs.