Solder Pad Voids Enhance Adhesion
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Solution Overview
Problem
Conventional methods for making solder pads do not adequately enhance the adhesion of solder balls to the pads, leading to reliability issues in the electrical, mechanical, and thermal connections between electronic components.
Innovation Solution
A method involving the formation of voids in the metal layer of the solder pad, followed by a second etching operation to create a solder pad with increased surface area contact, and a solder mask to protect and enhance adhesion, utilizing photo resist application and patterning techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional single-layer metal solder pad is used, then the manufacturing process is simple, but the adhesion of solder ball to the pad is insufficient
Solution Approach 1:
The patent introduces a porous layer between the metal solder pad and substrate, creating a hierarchical structure with voids at multiple scales. This porous architecture dramatically increases the contact area and mechanical interlocking between the solder ball and pad, resolving the adhesion problem while maintaining reasonable manufacturing complexity through selective etching processes.
Solution Approach 2:
The patent transitions from a conventional two-dimensional flat solder pad to a three-dimensional hierarchical structure with voids and porous features. This dimensional transformation creates multiple interfaces and contact points, significantly enhancing adhesion strength without proportionally increasing manufacturing complexity.
2Strength
If the contact area between solder pad and solder material is increased, then adhesion is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary patterning and etching operations to create the porous structure and voids in the metal layer before final solder pad formation. By preparing the enhanced surface area in advance, the subsequent solder deposition benefits from the pre-created adhesion features without requiring additional complex steps during the soldering process itself.
Solution Approach 2:
The manufacturing process is segmented into distinct stages: initial metal layer formation, selective etching to create voids, porous layer formation, and final pad definition. This segmentation allows each step to be optimized independently, managing overall process complexity while achieving the desired increased contact area for enhanced adhesion.
3Strength
If a hierarchical structure with voids is created in the metal layer, then mechanical interlocking is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes in the etching process, including controlled etch depth, etch rate, and selective etching conditions, to create the hierarchical void structure. By precisely controlling these etching parameters, the desired void sizes and distributions are achieved without requiring excessively tight tolerances across all manufacturing steps, thus managing manufacturing precision requirements.
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 increased contact area between the solder pad and solder material improves adhesion, reduces brittle fracture and solder ball drop, and enhances thermal and electrical conductivity, while the voids provide mechanical interlocking for stronger adhesion.
Implementation Method 1
A photo resist is applied to the metal layer and exposed through a photo mask placed over the photo resist
Implementation Method 2
The metal layer is selectively etched through the developed photo resist to form the solder pad
Data Source
AI summary
A method of making a solder pad includes providing a substrate having a metal layer formed on it, and applying a photo resist to the metal layer. The photo resist is patterned. A first etching operation is performed on the metal layer to form voids in the metal layer. A second etching operation is performed on the metal layer to form the solder pad. A solder mask is formed on the substrate and a portion of the solder pad.