Bowl Shaped Pad for Semiconductor Interconnects
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Solution Overview
Problem
Conventional substrates with flat pads have limited contact areas with solder, leading to unreliable interconnect joints, and existing solutions like underfill materials and glues are costly and difficult to control, limiting solder rework and increasing manufacturing costs.
Innovation Solution
The development of a bowl-shaped pad with non-uniform thickness, featuring a center region with a smaller thickness than the edge region, which can be formed using additive or subtractive processes, increasing the contact area with solder and potentially eliminating the need for underfill materials and glues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat pad with uniform thickness is used, then the manufacturing process is simple, but the contact area with solder is limited and interconnect joint reliability is reduced
Solution Approach 1:
The pad structure transitions from a flat surface to a bowl-shaped curved surface with non-uniform thickness. The curved profile increases the surface area available for solder contact while maintaining a manufacturable form factor. The bowl shape provides enhanced mechanical interlocking with solder balls without requiring complex multi-component assemblies.
Solution Approach 2:
The pad design adds vertical dimensionality by creating a non-uniform thickness profile with a center region thinner than the edge region. This dimensional change transforms a two-dimensional flat pad into a three-dimensional bowl-shaped structure, increasing the effective contact area with solder in the vertical dimension while preserving planar footprint constraints.
2Reliability
If underfill materials or glues are used to improve interconnect joint reliability, then joint reliability improves, but manufacturing costs increase and process control becomes suboptimal
Solution Approach 1:
The bowl-shaped pad structure inherently provides the reliability enhancement that previously required external underfill materials or glues. The geometric configuration of the pad itself creates improved solder contact and joint strength, eliminating the need for separate reliability-enhancing materials and their associated complex application processes.
Solution Approach 2:
The patent extracts and eliminates the need for underfill materials and glues from the manufacturing process. By designing the pad geometry to inherently provide improved joint reliability, the solution removes these additional materials and their complex application, curing, and rework processes entirely.
3Reliability
If underfill materials or glues are applied to improve interconnect joint reliability, then joint strength improves, but solder rework capability is limited
Solution Approach 1:
The bowl-shaped pad provides inherent joint reliability through its geometric design, eliminating dependence on external underfill or glue materials. This self-sufficient design allows for straightforward solder rework since no additional materials need to be removed or manipulated, and the pad structure itself maintains its integrity during rework operations.
Data Source
AI summary
Embodiments described herein provide techniques for forming an interconnect structure that includes a bowl shaped pad. 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 substrate (e.g., a semiconductor package, a PCB, etc.); and a metal pad over the substrate. The metal pad has a center region and an edge region. A thickness of the center region is smaller than a thickness of the edge region. A thickness of the center region may be non-uniform. The center region may have a bowl shape characterized by a stepped profile. The stepped profile is formed from metal layers arranged as steps. Alternatively, or additionally, the center region may have a bowl shape characterized by a curved profile. A pattern may be formed on or in a surface of the metal pad.