Conductive Pillar Package Structure for Low-Temperature Bonding
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Solution Overview
Problem
Conventional semiconductor packaging techniques face issues with bonding surface separation due to fatigue, reliability problems from defective solder, high contact resistance, and complex manufacturing processes, especially with copper structures requiring high temperatures and pressures, and incomplete underfill coverage affecting bonding quality.
Innovation Solution
A package structure and bonding method using conductive pillars and an adhesive layer between substrates, which reduces process requirements, manufacturing costs, and improves bonding quality by allowing low-temperature bonding with reduced stress and eliminating the need for chemical polishing and annealing, while ensuring favorable electrical connections and sealing protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper structure bonding is used to conduct bonding between chip and package carrier, then bonding strength is improved, but process complexity and manufacturing cost increase due to high temperature (300-450°C), high pressure (300 MPa), annealing process, and chemical polishing requirements
Solution Approach 1:
The patent changes the bonding parameters from high temperature (300-450°C) and high pressure (300 MPa) to low temperature and atmospheric pressure conditions. This is achieved by using a press-fitting method with conductive pillars that require minimal thermal and mechanical energy, thereby simplifying the overall bonding process while maintaining strong electrical and mechanical connections.
Solution Approach 2:
The patent extracts and eliminates unnecessary process steps from the conventional copper bonding method. Specifically, it removes the annealing process and chemical polishing steps by using conductive pillars with inherently flat surfaces that can be directly press-fitted without additional thermal treatment or surface preparation, significantly reducing process complexity.
2Manufacturing precision
If chemical polishing process is used to obtain flat surface on copper structure, then bonding quality is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent removes the chemical polishing step entirely from the manufacturing process. The conductive pillars are designed with inherently flat surfaces through the press-fitting method, eliminating the need for costly and complex chemical polishing processes while achieving the required surface flatness for high-quality bonding.
Solution Approach 2:
The patent uses a simple, cost-effective press-fitting method that creates sufficiently flat surfaces without requiring expensive chemical polishing equipment or materials. The conductive pillars are designed to achieve functional flatness through the bonding process itself, reducing manufacturing costs while maintaining adequate bonding quality.
3Volume of moving object
If underfill is used after bonding to reduce package size and refine contact points, then package compactness is improved, but bonding reliability may be reduced due to incomplete coverage of contact points
Solution Approach 1:
The patent performs the surface preparation and contact point formation actions before the bonding process itself. The conductive pillars are pre-formed with flat surfaces and precise geometries that ensure complete contact point coverage during press-fitting, eliminating the need for post-bonding underfill application and the reliability issues associated with incomplete coverage.
Solution Approach 2:
The conductive pillars serve as intermediaries that provide both mechanical support and electrical connection while ensuring complete contact between substrates. Their flat surfaces and precise geometries act as mediators that guarantee full contact point coverage, making the underfill process unnecessary and preventing reliability issues from incomplete coverage.
4Reliability
If solder balls are used for bonding, then electrical connection is achieved, but bonding surface separation occurs due to long-term fatigue and reliability issues arise from defective solder
Solution Approach 1:
The patent replaces solder balls with conductive pillars made of copper or copper alloys that are integrated into the substrate structure. These pillars provide permanent, fatigue-resistant electrical connections that do not suffer from the long-term reliability issues and defective solder problems associated with traditional solder ball bonding methods.
Solution Approach 2:
The conductive pillars are made of copper or copper alloys that combine excellent electrical conductivity with high mechanical strength and fatigue resistance. This composite material approach provides both reliable electrical connection and long-term bonding durability, overcoming the limitations of traditional solder ball materials.
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 method achieves strong and reliable bonding with improved electrical properties and reduced manufacturing complexity, enhancing the quality and reliability of the package structure through low-temperature assembly and simplified processing steps.
Implementation Method 1
an adhesive layer is disposed between the first substrate and the second substrate... The adhesive layer fills gaps between the conductive pillars
Implementation Method 2
Each of the conductive pillars electrically connects the pads and the second substrate... each of the conductive pillars electrically connects each of the dimples
Implementation Method 3
bonding between chip and package carrier in a press-fitting manner... suitable for a low temperature bonding assembly
Data Source
AI summary
A package structure includes a first substrate, a second substrate, a plurality of conductive pillars and an adhesive layer. The first substrate includes a plurality of vias and a plurality of pads. The pads are disposed on the first substrate, and fill the vias. The second substrate is disposed opposite to the first substrate. Each conductive pillar electrically connects each pad and the second substrate, and the adhesive layer fills the gaps between the conductive pillars. A bonding method of the package structure is also provided.