Miniature Cell Casing Seal Structure for Weld Heat Isolation
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Solution Overview
Problem
Miniature electrochemical cells with a size or total volume less than 0.5 cc face challenges in hermetically sealing the glass-to-ceramic and glass-to-metal seals due to thermal transfer during laser welding, which increases crack susceptibility.
Innovation Solution
A 'tongue and groove' construction is used to increase the bonded surface area between the base plate and annular sidewall, forming a hermetic glass-to-ceramic seal with the dielectric material, and an embossed rim on the lid absorbs energy during welding to prevent seal cracking, combined with an electrolyte fill port aligned with an annular space for efficient electrolyte distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to hermetically seal the lid to the annular sidewall in miniature cells, then the cell achieves hermetic closure, but thermal transfer to the glass seals increases their crack susceptibility
Solution Approach 1:
The base plate is segmented into distinct regions including a sealing surface, an annular groove, and a body portion. The sealing surface is specifically designed as a separate functional zone that interfaces with the glass seal, allowing thermal management to be optimized for this critical area during laser welding operations.
Solution Approach 2:
The annular groove functions as an intermediary thermal buffer between the laser welding zone and the glass seal. By positioning the groove between these elements, it absorbs and distributes thermal energy, preventing direct thermal transfer to the glass seal and reducing crack susceptibility while maintaining hermetic closure.
2Volume of moving object
If the distance from the weld site to the glass seal is reduced in miniature cells, then the cell size is minimized, but thermal energy transfer to the glass seals increases
Solution Approach 1:
The base plate incorporates regions with different thermal properties and geometries. The sealing surface has specific local characteristics optimized for glass seal bonding, while the annular groove provides localized thermal management. This local quality differentiation allows minimal cell volume while controlling thermal energy transfer to the glass seal during welding.
Solution Approach 2:
The annular groove introduces a dimensional feature that radially distributes thermal energy away from the glass seal interface. By utilizing this radial dimension for heat dissipation, the design accommodates reduced cell volume while preventing excessive thermal energy transfer to the seal in the axial welding direction.
3Ease of manufacture
If a conventional base plate design is used, then the manufacturing is simpler, but the bonded surface area between base plate and annular sidewall is insufficient
Solution Approach 1:
The annular groove serves multiple functions simultaneously: it provides mechanical retention for the glass seal, creates an annular channel for sealant or adhesive distribution, and acts as a thermal buffer during welding. This multi-functionality increases the bonded surface area without significantly complicating the manufacturing process.
Solution Approach 2:
The base plate is pre-formed with the annular groove and sealing surface features before the glass seal is applied. This preliminary structuring ensures optimal bonding geometry and surface area are already in place, facilitating subsequent sealing operations while maintaining manufacturing efficiency through integrated design rather than post-assembly modifications.
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 design enhances the structural integrity of the seals and ensures effective hermetic closure without compromising the glass seals, allowing for reliable operation and extended discharge in miniature cells.
Implementation Method 1
heated to a temperature that is sufficient to achieve a glass-to-ceramic seal with the dielectric material coating the annular sidewall and a glass-to-metal seal with the base plate
Implementation Method 2
heated to a temperature that is sufficient to achieve a glass-to-ceramic seal with the dielectric material coating the annular sidewall and a glass-to-metal seal with the base plate
Implementation Method 3
an embossed rim on the lid absorbs energy during welding to prevent seal cracking
Implementation Method 4
during laser welding of the lid to the annular sidewall, thermal transfer to the glass-to-ceramic seal and to the glass-to-metal seal that bond the base plate to the annular sidewall becomes challenging
Data Source
AI summary
A miniature electrochemical cell of a primary or secondary chemistry with a total volume that is less than 0.5 cc is described. The cell casing comprises an annular sidewall connected to a base plate opposite an upper lid. A sealing glass forms a hermetic glass-to-ceramic seal with a dielectric material contacting a lower portion of the annular sidewall and a glass-to-metal seal with the base plate. Since the glass seals against three surfaces of the annular sidewall, which are the inner and outer sidewall surfaces adjacent to the lower edge, the glass seal is robust enough to withstand the heat generated when the lid is welded to the upper edge of the annular sidewall. The lid has a sealed electrolyte fill port that is axially aligned with an annulus residing between the inner surface of the annular sidewall and the electrode assembly.