Bump Interconnection Segmented Solder Cap Alignment
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Solution Overview
Problem
Conventional solder bump interconnection methods face challenges with reduced pad pitch, leading to increased material costs, fabrication difficulties, and reliability issues due to solder bridging and short circuits during reflow-soldering in densely packed circuit boards.
Innovation Solution
A method and device for forming bump interconnection structures that include a metallization region on a substrate with a protective layer and a solder coupling element, where a metal bump and solder cap are used to form a bond between the substrates, optimizing the dimensions and ratios for improved alignment and bonding integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pad pitch is reduced to increase circuit density, then productivity and circuit functionality are improved, but manufacturing precision and reliability deteriorate due to solder bridging and misalignment
Solution Approach 1:
The solder joint is segmented into three distinct components: metal bump, solder cap, and solder resist opening. This segmentation allows each component to be optimized independently - the solder cap acts as a bridge between the metal bump and the pad, providing alignment tolerance and controlling solder flow to prevent bridging while maintaining high circuit density
Solution Approach 2:
The solder cap serves as an intermediary element between the metal bump and the solder resist opening. It mediates the alignment between these components, allowing the solder to flow controllably from the bump through the cap into the opening without bridging to adjacent pads, thus enabling reduced pad pitch while maintaining manufacturing precision
2Productivity
If pad pitch is reduced to increase circuit density, then productivity is improved, but reliability worsens due to solder bridging and short circuits
Solution Approach 1:
The solder resist opening is designed with specific local dimensions (smaller than conventional openings) and positioned precisely relative to the solder cap. This local optimization of the opening size and position controls solder flow locally at each joint, preventing bridging between adjacent pads while maintaining high circuit density, thus improving reliability
Solution Approach 2:
The solder cap is formed in advance during the fabrication process, establishing a predetermined geometry and position before the reflow soldering step. This preliminary formation of the cap structure pre-establishes the solder flow path and alignment references, ensuring reliable bonding even at reduced pad pitches where misalignment would cause bridging
3Productivity
If solder resist opening size is reduced to accommodate reduced pad pitch, then circuit density is improved, but manufacturing precision worsens due to difficulty in obtaining solder flow into openings
Solution Approach 1:
The solder cap acts as an intermediary that facilitates solder flow into the smaller opening. It provides a larger initial volume of solder that can be fed into the constrained opening space, ensuring adequate solder fills the small opening even when pad pitch is reduced and opening size is consequently reduced, thereby maintaining ease of manufacture
Solution Approach 2:
The dimensions of the solder cap and opening are optimized with specific parameter ratios (cap diameter to opening diameter, cap height to opening depth). By controlling these dimensional parameters, the invention ensures that solder can flow reliably into the smaller openings required for high circuit density, resolving the manufacturing difficulty while maintaining productivity
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
This approach enhances assembly yield and bond integrity by facilitating better solder alignment and flow into smaller openings, reducing material costs and reliability issues associated with reduced pad pitch.
Implementation Method 1
The solder cap is reflowed to bond the metal bump of the second workpiece to the solder coupling element of the first workpiece, forming a bump interconnection structure
Data Source
AI summary
The disclosure is directed to a device and method for manufacture thereof. The device includes a first workpiece bonded to a second workpiece by a bump interconnection structure. The bump interconnection structure allows for optimized packaging assembly yield and bond integrity.