Ceramic Wafer Heater Bonding Interface Elliptical Curvature
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Solution Overview
Problem
Conventional ceramic heating devices experience cracks near the bonded portion between the ceramic base and the support member due to thermal stress, which compromises their reliability.
Innovation Solution
A ceramic heating device with a hollow cylindrical support member bonded to the ceramic base, featuring a concave surface portion with an elliptical cross-section that connects the back surface of the ceramic base and the support member, where the ratio of the major axis radius to the minor axis radius is 1.5 or more, reducing thermal stress and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rounded portion is provided between the bonding surface of the ceramic base and the outer circumferential surface of the support member, then the smooth connection and crack suppression are improved, but thermal stress concentration still occurs at the rounded portion leading to crack expansion
Solution Approach 1:
The invention applies a curved surface (rounded portion) with specific geometric parameters (radius R1 and R2) to smoothly connect the ceramic base and support member. This curvature eliminates sharp corners that would concentrate stress, while the carefully controlled radius values ensure the curved surface does not become too flat (causing stress concentration) or too sharp (causing manufacturing issues and stress concentration). The curved surface distributes thermal stress evenly across the bonding interface.
Solution Approach 2:
The invention specifies precise parameter ranges for the rounded portion: radius R1 is 0.5-5mm and radius R2 is 1-10mm. By optimizing these geometric parameters, the design balances smooth connection (requiring larger radii) with stress distribution (requiring controlled radii). This parameter optimization resolves the contradiction by finding the sweet spot where the curved surface is smooth enough to prevent crack initiation but not so flat that it concentrates thermal stress.
2Reliability
If the ceramic base thickness is increased to prevent crack occurrence, then the structural integrity is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of uniformly increasing the entire ceramic base thickness, the invention applies local reinforcement only at the critical bonding interface between the ceramic base and support member. The rounded portion with optimized radii provides localized stress distribution exactly where thermal stress concentration occurs during heating/cooling cycles. This local quality approach prevents cracks at the bonding interface without requiring overall thickness increase, thereby maintaining manufacturing simplicity.
3Strength
If a rounded portion is provided to connect the ceramic base and support member, then the bonding strength is improved, but the manufacturing precision requirements increase due to the curved surface geometry
Solution Approach 1:
The invention defines specific, practical parameter ranges for the rounded portion (R1: 0.5-5mm, R2: 1-10mm) that balance bonding strength with manufacturability. These parameters are large enough to provide smooth stress distribution and strong bonding, yet small enough to be realistically manufactured with conventional ceramic processing techniques. The parameter optimization resolves the contradiction by selecting values that achieve both strong bonding and reasonable manufacturing precision requirements.
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 elliptical concave surface portion effectively suppresses crack occurrence, enhancing the reliability of the heating device by distributing thermal stress and maintaining structural integrity without increasing the ceramic base thickness, thus preventing internal defects and prolonged device lifespan.
Implementation Method 1
a resistance heating element embedded in the ceramic base
Implementation Method 2
one end surface is fixedly attached to an opposite surface of the ceramic base with the heating surface, that is, to a back surface thereof by solid-phase bonding or liquid-phase bonding
Data Source
AI summary
A heating device made of ceramics includes: a plate-like heating base having a heating surface; and a hollow cylindrical support member bonded to a back surface of the heating base. A concave surface portion that connects the back surface of the heating base and an outer surface of the support member smoothly to each other is formed in the vicinity of an outer end of a bonding interface between the heating base and the support member. On a cross section including an axis of the support member, the concave surface portion has a curved line of an arc of a ellipsoid in which a minor axis direction is parallel to an axis direction of the support member.