Irregular Terminal Pad Topography for Crack-Resistant Solder Joints
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Solution Overview
Problem
Solder joints in microelectronic component assemblies are prone to failure due to cracking and delamination at the interface between solder balls and terminal pads, especially under thermal cycling, as the interface has a limited surface area and is susceptible to mechanical stress, leading to open circuits.
Innovation Solution
The terminal pads are designed with an irregular surface topography featuring protruding and recess portions, which increase the bonding surface area and provide a mechanical interlock with solder balls, enhancing both metallurgical and mechanical strength, thereby preventing crack propagation and delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a planar terminal pad surface is used, then the manufacturing process is simple, but the bonding surface area is limited and the interface is susceptible to cracking and delamination under thermal cycling
Solution Approach 1:
The terminal pad surface is transformed from a planar geometry to an irregular topography with protruding and recess portions. This curvature modification increases the bonding surface area and creates a mechanical interlock effect with the solder ball, preventing crack propagation and delamination during thermal cycling while maintaining manufacturing feasibility through standard photolithography and etching processes
Solution Approach 2:
The invention transitions from a two-dimensional planar surface to a three-dimensional irregular surface by creating protruding portions extending above the original surface and recess portions extending below it. This dimensional transformation increases the effective bonding area without significantly increasing the pad footprint, thereby improving reliability without excessive complexity
2Strength
If the terminal pad bonding surface area is increased to prevent cracking, then the interface strength improves, but the terminal pad structure becomes more complex
Solution Approach 1:
The irregular surface topography with protruding and recess portions creates a mechanically interlocked structure that distributes stress more evenly across the bonding interface. This curvature-based design enhances interface strength by preventing crack initiation and propagation while maintaining a relatively simple overall pad structure that can be manufactured using conventional processes
Data Source
AI summary
An apparatus comprising a substrate having conductive traces and associated integral terminal pads on a surface thereof, the terminal pads having an irregular surface topography formed in a thickness of a single material of the conductive traces and integral terminal pads. Solder balls may be bonded to the terminal pads, and one or more microelectronic components operably coupled to conductive traces of the substrate on a side thereof opposite the terminal pads. Methods of fabricating terminal pads on a substrate, and electronic systems including substrates having such terminal pads are also disclosed.