Coin Cell PCB Assembly for Reflow Heat Resistance
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Solution Overview
Problem
Existing methods for manufacturing circuit board assemblies with coin-type secondary cells using reflow soldering result in deteriorated cell performance due to high-temperature processing.
Innovation Solution
The method involves optimizing the capacity and structure of the positive and negative electrodes in the coin-type secondary cell, using sintered plates with oriented primary particles and specific materials, and employing a gasket to ensure heat resistance and maintain high cell performance during reflow soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If reflow soldering is used to mount the coin-type secondary cell, then the manufacturing process is simplified, but cell performance deteriorates during heating
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by adding specific additives (vinylene carbonate at 5-20 wt% and fluoroethylene carbonate at 5-20 wt%) to modify the cell's thermal stability and reflow heat resistance, allowing the cell to maintain performance during reflow soldering heating
Solution Approach 2:
The patent creates a composite electrolytic solution system by combining multiple components (lithium salt, cyclic carbonate, chain carbonate, and additives) to achieve both manufacturing ease through reflow soldering and maintained cell performance, resolving the contradiction between process simplification and reliability
2Reliability
If the concentration of lithium salt in the electrolytic solution is increased to improve conductivity, then reactions with the positive active material are suppressed, but manufacturing cost and complexity increase
Solution Approach 1:
The patent optimizes the lithium salt concentration parameter to 0.5-2.0 mol/l and introduces additive concentration parameters (vinylene carbonate 5-20 wt%, fluoroethylene carbonate 5-20 wt%) to achieve the desired balance between conductivity, reaction suppression, and manageable complexity
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 approach allows for the production of a circuit board assembly with a coin-type secondary cell that retains high cell performance and capacity, suitable for reflow soldering, with improved lithium ion conductivity and reduced stress during heating.
Implementation Method 1
the oriented sintered plate includes a plurality of primary particles of a lithium composite oxide such as lithium cobaltate (LiCoO 2 ), and the primary particles are oriented to the plate surface of the positive electrode at an average orientation angle greater than 0° and less than or equal to 30°
Implementation Method 2
a coin-type secondary cell is mounted by reflow soldering on a wiring board
Implementation Method 3
reflow soldering
Implementation Method 4
by heat-treating the electrode at 200 °C to 450 °C, the degradation of battery characteristics is inhibited
Data Source
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AI summary
A circuit board assembly (8) includes a wiring board (81), a coin-type secondary cell (1) that is a lithium secondary cell electrically connected to the wiring board (81) by reflow soldering, and a wireless communication device (82) electrically connected to the wiring board (81). The coin-type secondary cell (1) includes a positive electrode including a sintered body, a negative electrode including a sintered body, an electrolyte layer provided between the positive electrode and the negative electrode, and a cell case having an enclosed space in which the positive electrode, the negative electrode, and the electrolyte layer are housed. When C is given as the capacity of the positive electrode and A is given as the capacity of the negative electrode, 1.03 < C/A < 1.60 is satisfied.