Dielectric Header Sub-Assembly Tapered Geometry Active Brazing
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Solution Overview
Problem
Conventional dielectric header sub-assemblies for high-temperature applications experience surface deformation and cracking due to thermal stresses, leading to issues with die performance and manufacturing complexity, particularly when brazing metallic parts to ceramic parts.
Innovation Solution
A dielectric header sub-assembly with a tapered portion on its outer periphery and a bore with varying opening sizes, utilizing an active braze filler material that maintains hermeticity and reduces deformation by remaining flat over a wide temperature range, eliminating the need for metallization or sputtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the header body is brazed to the metal ring at high temperature, then hermetic isolation is achieved, but compressive stresses cause surface distortion of the header
Solution Approach 1:
The patent applies a tapered portion to the outer periphery of the header body's second surface. This geometric parameter change creates a stress distribution profile that compensates for thermal expansion differences during brazing, allowing the first surface (where the die is mounted) to remain substantially parallel to the second surface over a wide temperature range (22°C to 1045°C), thereby maintaining surface flatness while achieving hermetic isolation.
2Manufacturing precision
If the header body is ground flat after brazing, then surface flatness is improved at room temperature, but deformities occur during temperature cycling
Solution Approach 1:
The tapered portion is incorporated into the header body design before brazing occurs. This preliminary geometric feature pre-compensates for thermal stresses that will occur during brazing and subsequent temperature cycling, eliminating the need for post-brazing grinding and preventing deformities during service temperature cycling.
3Ease of manufacture
If thick film ink coating is applied to ceramic for brazing, then metallization is achieved, but oxidation occurs at 400°C
Solution Approach 1:
The patent eliminates the need for thick film ink metallization coating on the ceramic header body by using an active braze filler material that can directly wet and bond to the ceramic surface. This removes the oxidizable metal layer while maintaining brazing capability, solving the oxidation resistance problem at elevated temperatures.
4Reliability
If sputtered metallic films are used for brazing, then oxidation resistance is improved, but wetting and capillary action become difficult and time-consuming
Solution Approach 1:
The patent uses an active braze filler material that acts as an intermediary between the metal components and the ceramic header body. This active filler material chemically reacts with the ceramic surface to create strong bonding and effective wetting without requiring sputtered metallic films, thereby maintaining oxidation resistance while significantly improving brazing efficiency and reducing cycle time.
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 significantly reduces deformation and cracking, enhances die performance by maintaining flatness under thermal stress, and simplifies the manufacturing process by using an active braze filler material that hermetically seals the components without requiring metallization.
Implementation Method 1
Sputtered metallic films can be used so that the braze filler can wet the surface of the ceramic by wicking along the joint via capillary action.
Implementation Method 2
an active braze filler material that hermetically seals the components
Implementation Method 3
The first surface and at least a portion the non-tapered portion of the second surface can be substantially parallel to each other over a range of temperatures, e.g. from 22 °C to 1045 °C.
Data Source
Figure 1~2
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Figure 5
AI summary
A dielectric header sub-assembly includes a header body (202) with opposed first (208) and second (210) surfaces and a side wall (212). The first and second surfaces define a header axis (A) extending therebetween. The side wall extends from the first surface to the second surface. The second surface includes a tapered portion (214). A dielectric header sub-assembly includes a bore (213). The bore extends from the first surface to the second surface. A first bore opening (224) of the bore proximate to the first surface is greater in area than a second bore opening (226) of the bore proximate the second surface. A method of assembling a header sub-assembly includes inserting an electrical connector (215) into a bore of a header body, applying an active braze filler material (228) into the bore and applying heat to braze the active braze filler material to the header body and the electrical connector.