Focal Plane Array Bump Structures with Segmented Profiles
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Solution Overview
Problem
Fine pitch, large format focal plane arrays require small interconnect bumps with large height to diameter ratios and minimal lateral expansion, making alignment and manufacturing yield challenging with traditional techniques, as lateral expansion affects the pressing process and limits pitch size.
Innovation Solution
A method involving dry etching of insulating material to create patterns for bump structures, depositing a seed layer, patterning with photo resist, and forming bumps with plating material, allowing for isolation and reduced lateral expansion to prevent electrical short circuits, using materials like copper or indium, and recessing the seed layer to create gaps between bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional interconnection techniques are used, then alignment is simpler, but manufacturing precision and reliability deteriorate due to lateral expansion causing electrical short circuits
Solution Approach 1:
The invention segments the bump structure into multiple functional zones: a narrower upper portion for electrical connection and a wider lower portion for mechanical stability. This segmentation allows the bump to maintain precise alignment while preventing lateral expansion from causing short circuits, as the expanded lower portion remains isolated from adjacent bumps.
Solution Approach 2:
The invention transitions from a two-dimensional circular bump profile to a three-dimensional structure with varying cross-sectional dimensions. The bump has a narrower width at the top surface and expands toward the base, utilizing the vertical dimension to resolve the contradiction between alignment precision and short circuit prevention.
2Length of moving object
If bump size is reduced for fine pitch applications, then pitch size decreases, but alignment difficulty increases due to smaller target area
Solution Approach 1:
The invention uses a non-circular bump profile where the width in the direction of pressing differs from the width in the direction of pitch. This dimensional differentiation allows smaller pitch sizes while maintaining adequate alignment area, as the alignment process可以利用 the larger dimension while the smaller dimension prevents short circuits.
Solution Approach 2:
The bump structure employs asymmetric dimensions with different widths in orthogonal directions. The larger width provides sufficient alignment target area, while the smaller width enables finer pitch spacing, resolving the contradiction between reduced pitch size and alignment difficulty.
3Reliability
If bump height to diameter ratio is increased, then electrical connection improves, but lateral expansion control becomes more difficult
Solution Approach 1:
The bump structure is segmented into distinct vertical zones with different lateral dimensions. The upper portion maintains a narrower width for precise electrical connection, while the lower portion expands to provide mechanical support. This segmentation allows high height-to-diameter ratio while controlling lateral expansion through the isolated wider base.
Solution Approach 2:
The invention utilizes the vertical dimension to achieve high electrical connection reliability through increased height, while simultaneously controlling lateral expansion by varying the horizontal dimension along the height. The expanding profile toward the base confines lateral growth away from adjacent bumps.
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
Enables the formation of bump structures with superior properties, such as reduced size and increased height to diameter ratio, without short circuiting, facilitating smaller pixel pitch sizes and improved manufacturing yield.
Implementation Method 1
dry etching a layer of insulating material to create a pattern for bump structures
Implementation Method 2
forming bump structures over the seed layer and the photo resist material with a plating material to form bump structures in the pattern
Data Source
AI summary
A method of forming bump structures for interconnecting components includes dry etching a layer of insulating material to create a pattern for bump structures. A seed layer is deposited on the insulating material over the pattern. The seed layer is patterned with a photo resist material. The method also includes forming bump structures over the seed layer and the photo resist material with a plating material to form bump structures in the pattern, wherein the bump structures are isolated from one another.