Semiconductor Package Solder-on-Pad Structure for Fine Pitch
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Solution Overview
Problem
Current semiconductor packaging technologies face challenges in achieving smaller form factors, higher chip integration, and reliable solder joints due to limitations in solder pad spacing and assembly processes.
Innovation Solution
The development of self-supporting solder-on-pad structures that allow for finer pitch solder joints and reduced pad margins, enabling smaller package form factors and improved reliability by using discrete solder material deposited on pads, which can be reflowed for bonding without additional retaining materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder ball array packaging is used, then electrical communication between package and PCB is achieved, but pad spacing must be large requiring oversized pads and additional retaining materials
Solution Approach 1:
The solder connection is segmented into discrete solder balls positioned on pads, where each solder ball serves as an independent connection element. This segmentation allows pads to be smaller and closer together, as each pad only needs to support its own solder ball rather than providing lateral support across a large area.
Solution Approach 2:
The solder ball acts as an intermediary element between the pad and the PCB trace. Instead of requiring direct large-area contact between pad and PCB, the solder ball mediates the connection, enabling smaller pad dimensions while maintaining reliable electrical and mechanical connection.
2Volume of moving object
If smaller form factors are achieved through reduced pad spacing, then chip integration is improved, but solder joint reliability deteriorates due to insufficient pad support
Solution Approach 1:
The invention changes the geometric parameters of the solder connection by forming solder balls with specific diameter ratios relative to pad size (solder ball diameter approximately 0.5-2 times the pad diameter). This parameter optimization ensures adequate mechanical support and thermal coupling for reliable solder joints even with reduced pad spacing.
Solution Approach 2:
The solder connection transitions from a flat planar interface to a spherical solder ball geometry. This curvature provides superior mechanical interlocking, thermal coupling, and stress distribution compared to flat solder joints, enhancing reliability in compact packages with reduced pad spacing.
3Manufacturing precision
If discrete solder material is deposited on pads, then finer pitch solder joints are achieved, but additional retaining materials and processes are required
Solution Approach 1:
The solder material is applied as discrete balls that are self-positioning on the pads through controlled dispensing or placement processes. The solder balls inherently maintain their position and shape without requiring additional retaining structures or complex alignment mechanisms, simplifying the overall assembly process while achieving fine pitch.
4Reliability
If conventional soldering processes are used, then solder joints are formed, but oversized pads and additional retaining materials are needed to prevent solder defects
Solution Approach 1:
The solder is pre-formed into discrete balls with controlled size and shape before placement on the pads. This preliminary preparation ensures that the solder has optimal geometry for bonding, eliminating the need for oversized pads or retaining materials to prevent common solder defects such as bridging, insufficient wetting, or cold joints.
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 results in increased chip integration, improved functional performance, and reduced defects by minimizing pad spacing and eliminating the need for oversized pads and additional retaining materials, leading to more efficient and reliable semiconductor packages.
Implementation Method 1
The solder material is then reflowed such that the solder-on-pad structure changes from a solid state to a liquid or semi-liquid state, thereby bonding (physically and electrically) the circuit element to the pad
Data Source
AI summary
A semiconductor package and methods for producing the same are described. One example of the semiconductor package is described to include a substrate having a first face and an opposing second face. The package is further described to include a plurality of pads disposed on the first face of the substrate, each of the plurality of pads including a first face and an opposing second face that is in contact with the first face of the substrate. The semiconductor package is further described to include a plurality of solder-on-pad structures provided on a first of the plurality of pads.