Reinforcement Layer Structure for Low-Warpage Flip-Chip Packages
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Solution Overview
Problem
The use of wirebond packages in semiconductor devices results in increased thickness and processing costs, and thin, flexible substrates are unable to utilize flip-chip bonding due to deformation during mass reflow and high costs associated with thermal compression bonding.
Innovation Solution
A reinforcement layer is formed over the tape substrate to increase stiffness, allowing for flip-chip ball grid array (FCBGA) bonding without specialized handling equipment, using mass reflow without warpage and enabling standard flip-chip processing equipment to be used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wirebond packaging is used, then interconnect reliability is achieved, but package thickness increases and processing costs increase
Solution Approach 1:
The patent replaces the mechanical wirebonding system with a flip-chip bonding system that uses solder bumps and reflow soldering. This substitution eliminates the need for wire bonds extending from the die surface, thereby reducing package thickness while maintaining interconnect reliability through direct die-to-substrate solder joints.
Solution Approach 2:
The patent changes the bonding parameters from mechanical wire attachment to thermal reflow soldering. By controlling the reflow temperature profile and using compliant substrates, the process achieves reliable solder joint formation without requiring the additional thickness needed for wirebond structures.
2Length of stationary object
If flip-chip bonding is used on thin substrates, then package thickness is reduced, but substrate warpage occurs during mass reflow
Solution Approach 1:
The patent applies a reinforcement layer to the thin substrate before the flip-chip bonding process. This reinforcement layer acts as a cushioning element that prevents substrate warpage during mass reflow by providing additional structural support and distributing the thermal stress uniformly across the substrate surface.
Solution Approach 2:
The patent creates a composite structure by combining the thin substrate with a reinforcement layer. This composite material approach allows the substrate to maintain its thin profile for reduced package thickness while the reinforcement layer provides the necessary stiffness to prevent warpage during thermal processing.
3Shape
If thermal compression bonding is used instead of mass reflow, then substrate warpage is reduced, but processing cost increases
Solution Approach 1:
The reinforcement layer serves as a preventive measure that allows the use of cost-effective mass reflow processing without suffering from warpage issues. This eliminates the need for expensive thermal compression bonding equipment and processing, as the reinforcement layer already prevents warpage before the bonding process begins.
Solution Approach 2:
The patent uses a relatively simple and inexpensive reinforcement layer that enables the use of standard, cost-effective mass reflow equipment. This approach avoids the need for expensive thermal compression bonding machinery, making the process economically viable for high-volume production.
4Adaptability or versatility
If specialized substrate handling systems are used for thin substrates, then flip-chip bonding capability is achieved, but device complexity and cost increase
Solution Approach 1:
The reinforcement layer is applied beforehand to provide structural support to the thin substrate. This allows standard, simple substrate handling equipment to be used during flip-chip bonding, as the reinforcement layer prevents substrate deformation and eliminates the need for specialized handling systems designed for flexible substrates.
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 solution reduces warpage and handling difficulties of thin substrates, enabling cost-effective flip-chip bonding on flexible substrates while maintaining package quality and reducing processing complexity.
Implementation Method 1
A reinforcement layer is formed over the tape substrate to increase stiffness
Implementation Method 2
bonding the device die to the substrate by reflowing one or more solder bumps
Data Source
AI summary
Embodiments of the invention include device packages and methods of forming such packages. In an embodiment, the method of forming a device package may comprise forming a reinforcement layer over a substrate. One or more openings may be formed through the reinforcement layer. In an embodiment, a device die may be placed into one of the openings. The device die may be bonded to the substrate by reflowing one or more solder bumps positioned between the device die and the substrate. Embodiments of the invention may include a molded reinforcement layer. Alternative embodiments include a reinforcement layer that is adhered to the surface of the substrate with an adhesive layer.