TAB Package Outer Lead Width Variation for Crack Resistance
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Solution Overview
Problem
Conventional TAB packages face reliability issues due to mechanical stress from folding motions, which can lead to cracking of outer lead portions, particularly in applications like LCD displays where flexible connections between host device elements are required.
Innovation Solution
The design incorporates a TAB package with outer lead portions featuring an end portion, a terminal portion, and a transition portion with varying widths, where the transition portion overlays the edge region of the glass panel, providing increased mechanical strength and resistance to bending-induced fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional TAB packages use uniform width outer lead portions, then manufacturing is simple, but mechanical strength is insufficient and cracking occurs under folding stress
Solution Approach 1:
The outer lead portions are designed with non-uniform width, featuring a wider terminal portion and a narrower end portion. This local variation in geometry provides enhanced mechanical strength at the terminal portion where it connects to the semiconductor die, while maintaining flexibility at the end portion. The transition portion gradually changes the width between these two regions, creating a stress distribution that prevents cracking under folding motions.
2Strength
If outer lead portions are made thicker to increase strength, then resistance to cracking improves, but flexibility and ease of bonding deteriorates
Solution Approach 1:
The end portion of the outer lead portions is designed with a narrower width compared to the terminal portion. This narrower end portion maintains flexibility and ease of bonding to the connection surface, while the wider terminal portion provides the necessary mechanical strength. The gradual transition between these portions optimizes both bonding ease and fracture resistance.
3Reliability
If transition portion overlays edge region of glass panel, then mechanical strength under stress is enhanced, but alignment precision requirements increase
Solution Approach 1:
The transition portion is designed to overlay the edge region of the glass panel connection surface in advance, creating a predetermined stress distribution pattern. This preliminary positioning of the wider transition portion over the edge region prepares the structure to better withstand folding stresses before they occur, enhancing long-term reliability.
Data Source
AI summary
A device is provided in which a glass panel having beveled edge is flexibly connected to a TAB package. The outer lead portions of the TAB package include an end portion of first width connected to a connection pattern on the glass panel, a terminal portion having a second width greater than the first width, and a transition portion having a width that varies between the first and second widths. When the TAB package is connected the transition portion of the respective outer lead portions are disposed over the beveled edge of the glass panel.