Symmetric Oxygen Sensor Chip Structure for Stress-Balanced Sintering
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Solution Overview
Problem
Existing oxygen sensor chip production technologies face issues such as layering, cracking, and bending due to material shrinkage mismatches and thermal stress, leading to high defect rates and instability in bonding.
Innovation Solution
A symmetric four-layer structure is introduced, with zirconia substrate layers sandwiched by alumina insulating layers and a heater layer at the center, along with the use of 5 mol yttria-stabilized zirconia and optimized additives like mullite and alumina to enhance thermal conductivity and stress symmetry, combined with a manufacturing process involving slurry preparation, lamination, and controlled sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a three-layer asymmetric structure with alumina insulating layer and zirconia substrate layer is used, then the chip can be manufactured with existing technology, but bending deformation and cracking occur due to uneven stress and shrinkage mismatch during sintering
Solution Approach 1:
The patent applies asymmetry in reverse by creating a symmetric four-layer structure where the top and bottom halves are mirror images. This symmetry balances the thermal and mechanical stress distribution during sintering, preventing the bending deformation and cracking that occur in asymmetric three-layer structures. The symmetric arrangement ensures uniform shrinkage and stress distribution, eliminating the manufacturing precision issues caused by material mismatches.
Solution Approach 2:
The patent segments the traditional three-layer structure into four separate substrate layers (first, second, third, and fourth substrate layers) with insulating and heater layers positioned between them. This segmentation allows for better stress management and more uniform thermal distribution during sintering, preventing the concentration of stress that leads to cracking and deformation in the conventional three-layer design.
2Strength
If high-temperature sintering is performed to bond the layers, then the bonding strength is improved, but excessive melting and unstable bonding occur due to high shrinkage rates and thermal stress
Solution Approach 1:
The symmetric four-layer structure distributes thermal stress uniformly during high-temperature sintering, preventing localized overheating and excessive melting. The mirror-image arrangement ensures that stress from the top and bottom offsets each other, maintaining bonding stability while achieving sufficient bonding strength through controlled thermal processing.
Solution Approach 2:
The patent modifies the structural parameters by transitioning from a three-layer to a four-layer configuration, which changes the thermal and mechanical parameter distribution during sintering. This structural parameter change allows for more controlled heat distribution and stress management, achieving reliable bonding without excessive melting or instability.
3Strength
If the sintering temperature is increased to improve bonding, then the bonding strength increases, but natural bending and cracking increase due to shrinkage mismatch between alumina and zirconia
Solution Approach 1:
The symmetric structure eliminates the shrinkage mismatch problem by arranging identical material layers (zirconia substrate layers) at both the top and bottom, with insulating and heater layers in between. This symmetry ensures that thermal expansion and contraction forces are balanced, preventing bending and cracking even at high sintering temperatures while maintaining strong bonding.
Solution Approach 2:
The symmetric arrangement of substrate and insulating layers creates a counterbalancing effect where stress from the top half offsets stress from the bottom half during sintering. This counterweight effect prevents the accumulation of stress that would otherwise cause bending and cracking, allowing high-temperature processing to achieve strong bonding without harmful deformations.
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 symmetric structure and material composition significantly reduce bending and cracking, improving product yield and quality by ensuring uniform stress distribution and thermal stability, with enhanced hardness, fracture toughness, and flexural strength.
Implementation Method 1
the shrinkage mismatch problem can occur due to the different shrinkage rates of the materials, so that serious layering, cracking or extremely low yield can be caused; or because the materials of the joint part are different, the high-temperature melting performance of the joint part has quite large difference
Implementation Method 2
When the chip is sintered and formed at a high temperature of 1450 degrees, due to the different shrinkage rates of alumina and zirconia at high temperatures, it is easy to cause natural bending of the chip
Implementation Method 3
the use of 5 mol yttria-stabilized zirconia and optimized additives like mullite and alumina to enhance thermal conductivity and stress symmetry
Implementation Method 4
it is also prone to cracking during thermal expansion and contraction
Implementation Method 5
a manufacturing process involving slurry preparation, lamination, and controlled sintering
Data Source
AI summary
Disclosed are a symmetric structural type oxygen sensor chip and its manufacturing method. The chip comprises a substrate layer, an insulating layer, and a heater layer; the substrate layer and the insulating layer constitute a tightly combined symmetrical structure with the heater layer as the axis of symmetry, no matter in the stress release during the sintering and forming process, or in the thermal expansion and contraction stress release during the subsequent use process, a relatively symmetrical and uniform stress release can be formed, the warpage of the chip is greatly improved, and the deformation of the chip can be basically controlled within 0.1 mm, which greatly reduces the chipping phenomenon during the assembly process, and can also reduce the cracking phenomenon during the use process.