Battery Tab Bonding in Microelectronic Packages at Low Temperature
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Solution Overview
Problem
Existing semiconductor devices face challenges in integrating non-rechargeable lithium button batteries internally due to size constraints and temperature sensitivity, leading to reliability issues and interruptions in high-volume production processes.
Innovation Solution
A low-temperature manufacturing process integrates button batteries into semiconductor packages using conductive bonding agents and encapsulation methods that form cavities for battery tabs, ensuring electrical and mechanical connections without degrading battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If button batteries are externally mounted via sockets, tabs or clips, then the battery can be installed after fabrication, but the device bulk increases and reliability decreases
Solution Approach 1:
The patent merges the battery mounting process with the encapsulation process by integrating battery tabs into the mold cavity structure. The battery is positioned within the mold cavity before encapsulation, allowing the encapsulant to simultaneously protect both the semiconductor device and the battery while establishing electrical connections through the same molding operation.
Solution Approach 2:
The battery is nested within the encapsulated volume of the semiconductor package. The mold cavity is designed to accommodate the battery in a recessed position, allowing the battery to be embedded within the overall package structure rather than mounted externally, thus reducing bulk while maintaining integration.
2Ease of manufacture
If button batteries are externally mounted, then installation is simplified, but the assembly flow is interrupted in high-volume production
Solution Approach 1:
The patent combines multiple operations into a single encapsulation step: semiconductor device mounting, battery positioning, electrical connection establishment, and protective encapsulation all occur during the same molding cycle. This eliminates the need for separate battery mounting steps that would interrupt high-volume production assembly flow.
3Ease of manufacture
If conventional encapsulation processes are used, then standard manufacturing is maintained, but battery performance is degraded
Solution Approach 1:
The patent applies different temperature conditions to different regions of the encapsulation process. The mold cavity and battery interface are designed to maintain low temperatures specifically where the battery is located, while other parts of the encapsulation process can proceed at conventional temperatures. This localized temperature control protects battery performance while maintaining overall process efficiency.
Solution Approach 2:
The patent modifies the encapsulation process parameters, specifically the temperature, to be compatible with battery requirements. By changing the encapsulation temperature from conventional high temperatures to low temperatures, the process maintains battery performance while still achieving proper encapsulation and electrical connections.
4Ease of manufacture
If high-temperature processes are used for encapsulation, then standard materials can be used, but battery performance degrades
Solution Approach 1:
The patent changes the temperature parameter of the encapsulation process from conventional high temperatures to low temperatures specifically to protect the battery. This parameter change enables the use of standard encapsulation materials and processes while maintaining battery performance by ensuring the temperature remains below the battery's degradation threshold throughout the encapsulation cycle.
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 solution allows for reliable internal battery integration, maintaining battery performance and compatibility with high-volume production processes by using low-temperature materials and methods.
Implementation Method 1
A low temperature, conductive bonding agent, such as electrically conductive adhesive (ECA), is deposited into the channels formed by the cavities and apertures
Implementation Method 2
the package and mounted battery are encapsulated or coated using a low-temperature encapsulant or conformal coating
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3A
AI summary
A self-powered microelectronic semiconductor device includes low temperature interconnection and encapsulation materials to enable integration of a battery with the microelectronics package during manufacture. The package includes a partially exposed leadframe or leads of a substrate for connecting the battery. The battery includes one or more terminal connectors that can either be manufactured by the battery vendor or externally attached using spot/laser or resistance welding. The steps of connecting the battery to the package are performed after the microelectronic package assembly to ensure the battery does not experience any high temperatures from the package assembly process. Cavities are formed in an overmolded molding compound to expose the leadframe or battery pads for electronic connection. A low temperature electrically conductive bonding agent is used to create the electrical and mechanical bond of the battery tabs to the leadframe. A low temperature encapsulant is then applied over the package and mounted battery.