Combing Bump Structure for Fine-Pitch Adhesion
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Solution Overview
Problem
Current low-cost Redistribution Layer (RDL)/Bumping solutions struggle with processing fine-pitch products due to the low adhesive strength of PI (polyimide) materials, which can lead to peeling issues during the wafer processing, especially when improperly controlled.
Innovation Solution
A combing bump structure is developed, featuring a semiconductor substrate with a pad, a conductive layer, a solder bump, and metal side walls along its laterals, along with metal pins within the bump, to enhance joint strength through a reflow process, using a manufacturing method that includes forming pads, conductive layers, solder bumps, and metal side walls to create a robust solder joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-cost RDL/Bumping solution is used, then manufacturing cost is reduced, but adhesive strength deteriorates causing peeling issues
Solution Approach 1:
The patent employs a composite structure consisting of multiple metal layers (first metal layer, second metal layer, third metal layer) with different properties. The first metal layer provides adhesion to the substrate, the second metal layer provides solderability, and the third metal layer enhances mechanical strength and oxidation resistance. This composite material approach resolves the contradiction by achieving both low cost and high adhesive strength through material composition rather than relying on expensive single-material solutions.
Solution Approach 2:
The patent divides the bump structure into multiple functional segments: the first metal layer segment for adhesion, the second metal layer segment for solderability, and the third metal layer segment for strength enhancement. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between cost and adhesive strength by distributing functions across multiple layers rather than requiring a single expensive material to perform all functions.
2Ease of operation
If PI material is used as buffer layer, then ease of processing is improved, but adhesive strength deteriorates
Solution Approach 1:
The patent introduces metal layers as intermediary elements between the PI buffer layer and the solder bump. The first metal layer acts as an intermediary that bonds to both the PI layer and the solder, providing mechanical anchoring and chemical bonding interfaces. This intermediary structure resolves the contradiction by compensating for the PI material's low adhesive strength through the metal layer's superior bonding capabilities, maintaining ease of processing while enhancing overall adhesion.
3Manufacturing precision
If fine-pitch products are processed, then product precision is improved, but reliability deteriorates due to peeling issues
Solution Approach 1:
The patent uses a composite metal layer structure where the third metal layer specifically addresses reliability concerns for fine-pitch applications. This layer provides enhanced mechanical strength and oxidation resistance, which are critical for maintaining joint integrity in fine-pitch products where peeling issues are more prevalent. The composite structure allows fine-pitch processing while compensating for reliability weaknesses through material properties.
Solution Approach 2:
The patent extends the solution from a single-layer to a multi-layer vertical structure, adding the dimension of layer thickness and composition control. By controlling the thickness and material properties of each metal layer, the patent achieves both fine-pitch horizontal precision and vertical reliability through the multi-dimensional structure, resolving the contradiction between manufacturing precision and joint reliability.
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
The proposed structure and method improve the adhesive strength and reliability of solder joints, enabling the processing of fine-pitch products by ensuring the metal side walls and pins contribute to enhanced joint integrity during the reflow process, addressing the weakness of PI materials.
Implementation Method 1
the second solder bump configured to form a solder joint with the first solder bump when the first and second solder bumps are brought together and a reflow process is performed
Data Source
AI summary
A manufacturing method of a combing bump structure is disclosed. In the manufacturing method, a semiconductor substrate is provided, a pad is formed on the semiconductor substrate, a conductive layer is formed on the pad, a solder bump is formed on the conductive layer, and at least two metal side walls are formed disposed along opposing laterals of the solder bump respectively.