IC Lead Structure Necking Design for Fine Pitch Etching
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Solution Overview
Problem
The narrow gaps between adjacent leads in integrated circuit (IC) packaging make it difficult for etchants to enter, leading to challenges in etching and forming lead structures, which limits chip design and production yield, especially when trying to meet fine pitch requirements.
Innovation Solution
A lead structure with a necking design that increases the gap between adjacent leads by having a first lead segment with a smaller width than its bump connecting part, and a second lead segment with a similar design, allowing for staggered arrangement of bump connecting parts to further increase the gap, facilitating stable etching and compliance with fine pitch requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gaps between adjacent leads are narrowed to increase lead count in confined space, then the lead count increases, but the etching process becomes difficult or impossible due to insufficient gap width
Solution Approach 1:
The lead structure is segmented into multiple parts: a bump connecting part, a lead segment, and an optional second lead segment. This segmentation allows each part to have optimized dimensions, particularly making the lead segment narrower than the bump connecting part, which increases the gap between adjacent leads while maintaining structural integrity and enabling etchant access.
Solution Approach 2:
Different parts of the lead structure have different width characteristics. The bump connecting part has a larger width for mechanical strength and electrical connection, while the lead segment has a smaller width to increase spacing. This local variation in quality allows the structure to simultaneously satisfy strength requirements and etching accessibility requirements.
2Ease of manufacture
If the minimum pitch of lead structure is set to 20 μm to ensure sufficient gaps for adjacent leads, then the etching process is feasible, but the lead count in limited circuit space is reduced
Solution Approach 1:
The invention utilizes the vertical dimension by staggering the arrangement of bump connecting parts of adjacent leads in the vertical direction. This three-dimensional arrangement allows the lead segments to be positioned such that gaps between them are increased, effectively reducing the pitch requirement while maintaining etching accessibility.
Solution Approach 2:
By dividing the lead structure into bump connecting parts and lead segments with different widths, the invention achieves an effective pitch reduction. The narrower lead segments create larger gaps between adjacent leads, allowing pitch to be reduced below 20 μm while still enabling proper etching process.
3Length of moving object
If the width of lead segment is reduced to increase gap between adjacent leads, then the gap increases and etching becomes feasible, but the structural strength may be compromised
Solution Approach 1:
The lead structure employs local quality variation where the bump connecting part has larger width for strength and electrical connection, while the lead segment has smaller width for spacing. This localized differentiation allows the narrow lead segment to provide sufficient gap width without compromising overall structural strength, as the stronger bump connecting parts compensate for the weaker narrow segments.
Solution Approach 2:
Segmenting the lead into functional parts with different dimensions allows optimization of each part's properties. The bump connecting part is designed for mechanical and electrical strength, while the lead segment is designed for spacing, enabling the structure to achieve both strength and gap width requirements simultaneously.
Data Source
AI summary
The present invention discloses a lead structure of the circuit, which comprises a first lead and a second lead. The first lead includes a first bump connecting part and a first lead segment. The first lead segment is connected to the first bump connecting part. The width of the first lead segment is smaller than the width of the first bump connecting part. The second lead is adjacent to the first lead and there is a lead gap therebetween. The second lead also includes a second bump connecting part and a first lead segment. The first lead segment of the second lead is connected to the second bump connecting part. The second bump connecting part and the first bump connecting part are arranged staggeredly. The second bump connecting part is adjacent to the first lead segment of the first lead.