Micro-Featured Pad Structure for Thermal Fatigue-Resistant Solder Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing mismatch in coefficients of thermal expansion (CTE) between semiconductor packages and printed circuit boards (PCBs) leads to stress on interconnect joints, reducing their reliability due to limited adherence of solder to conventional flat interconnect structures, and existing solutions like underfill materials and glues are costly and suboptimal.
Innovation Solution
The formation of interconnect structures with micro features on pads, which increase the surface area for solder adherence, allowing the interconnect joints to absorb stress and potentially eliminate the need for underfill materials or glues, by creating a profile for the solder to conform to and enhancing thermal fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flat interconnect structures are used, then manufacturing is simple, but solder adherence is limited and interconnect joint reliability is reduced
Solution Approach 1:
The patent applies curvature by forming micro features (protrusions and recesses) on the pad surface, transforming the flat surface into a three-dimensional profile. This curved/structured surface increases the effective surface area for solder adherence, allowing the interconnect joint to better absorb stress from CTE mismatches, thereby improving reliability without requiring underfill materials or glues.
2Reliability
If underfill materials or glues are used to improve interconnect joint reliability, then adherence is enhanced, but manufacturing cost and complexity increase
Solution Approach 1:
The patent implements self-service by designing the pad structure itself to provide the adherence enhancement normally requiring external materials. The micro features on the pad surface directly increase solder adherence and stress absorption capability, eliminating the need for underfill materials or glues. This self-service approach maintains reliability improvement while avoiding the added manufacturing complexity and cost of applying and managing external adhesive materials.
3Strength
If pad surface area is increased through micro features, then solder adherence is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by modifying the pad surface topology through micro features with specific dimensional parameters (protrusions and recesses). These controlled geometric changes increase the effective surface area for solder adherence, enhancing joint strength. The micro features are fabricated using standard semiconductor processing techniques, maintaining compatibility with existing manufacturing capabilities while achieving the desired parameter optimization for improved adherence.
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 the reliability of interconnect joints by increasing adherence and reducing stress concentrations, thereby improving the life cycles of packages and electronic devices while minimizing costs and manufacturing complexities.
Implementation Method 1
CTE mismatches create stress between interconnect joints coupling packages and PCBs. Such stress can curtail the reliable functioning of a packaged system because the stress may damage the interconnect joints.
Data Source
AI summary
Embodiments described herein provide techniques for forming an interconnect structure that includes micro features formed therein. Such embodiments can assist with improving interconnect joint reliability when compared to conventional pads that have a flat surface. An interconnect structure may comprise: a metal pad over a substrate (e.g., a semiconductor package, a PCB, an interposer, etc.). Micro features may be formed in an edge of the metal pad or away from the edge of the metal pad. The micro features can assist with: (i) increasing the contact area between solder used to form an interconnect joint and the metal pad; and (ii) improving adherence of solder used to form an interconnect joint to the metal pad. These benefits can improve interconnect joint reliability by, among others, improving the interconnect joint's ability to absorb stress from substrates having differing coefficients of thermal expansion.