Active Soldering for Metal-Ceramic Sensor Contacts
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Solution Overview
Problem
Conventional soldering methods for electronic assemblies on ceramic substrates are mechanically unstable and fail to utilize the high temperature resistance of ceramics, as they melt at lower temperatures and do not provide a robust mechanical connection, making them prone to failure under mechanical stress.
Innovation Solution
The use of active soldering with a metallic contact in the form of a pin inserted into a blind hole in the ceramic substrate, which creates both an electrical and mechanical connection through sintering and chemical bonding with the ceramic, utilizing a suitable metal alloy that reacts with the ceramic surface at high temperatures to form a strong bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional soft soldering is used to connect metal contacts to ceramic substrates, then the soldering process is simple and low-cost, but the joint lacks mechanical strength and cannot utilize the high temperature resistance of ceramics
Solution Approach 1:
The patent changes the soldering temperature parameter from conventional soft soldering (200-300°C) to active soldering (above 450°C, typically 850-950°C). This parameter change enables the use of active solder alloys that form strong metallurgical bonds with ceramic substrates, simultaneously achieving high joint strength and utilizing the ceramic's temperature resistance
Solution Approach 2:
The patent uses composite solder alloys containing reactive metal elements (such as Ti, Nb, Ta) combined with base metals (Sn, Ag, Cu). These composite materials enable direct chemical bonding with ceramic surfaces while maintaining mechanical strength and electrical conductivity, resolving the contradiction between ease of manufacture and joint strength
2Ease of manufacture
If conventional soft soldering is used to connect metal contacts to ceramic substrates, then the manufacturing process is simple, but the connection is mechanically unstable and prone to failure under shock and vibration
Solution Approach 1:
By changing the soldering temperature to above 450°C and using active solder alloys, the patent creates joints with metallurgical bonding strength that can withstand shock and vibration, while the manufacturing process remains relatively simple and suitable for industrial production
Solution Approach 2:
The active solder acts as an intermediary material that chemically bonds to both the metal contact and the ceramic substrate, creating a tri-metal-ceramic interface. This intermediary enables strong mechanical connections that resist shock and vibration while maintaining electrical conductivity
3Temperature
If conventional soldering is used, then low temperature processing is achieved, but the high temperature resistance advantage of ceramics cannot be utilized
Solution Approach 1:
The patent raises the soldering temperature parameter to above 450°C (typically 850-950°C), which matches the ceramic substrate's temperature capabilities. This enables the ceramic's high temperature resistance to be fully utilized in the final application while the soldering process itself operates at temperatures the ceramic can withstand
4Strength
If active soldering is used to create strong mechanical bonds between metal and ceramic, then joint strength and temperature resistance are improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies flux and positions the active solder alloy on the metal contact before the soldering process. This preliminary preparation ensures proper wetting and bonding when the high temperature is applied, simplifying the overall process by pre-configuring the bonding interface
Solution Approach 2:
The active solder alloy serves as a mediator that simplifies the metal-ceramic bonding process by providing automatic wetting and chemical bonding capabilities. This eliminates the need for complex surface preparation steps like metallization or adhesion promoters, reducing manufacturing complexity while achieving strong joints
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 method produces a sensor with a stable, high-temperature-resistant metal-ceramic connection that is robust against mechanical stress and environmental influences, ensuring reliable electrical and mechanical anchoring of the sensor element within the ceramic substrate.
Implementation Method 1
A special form of hard soldering is active soldering. Commercially available active solders have a melting point of approximately 850°C. Furthermore, it is advantageous that active soldering allows metal to be soldered directly onto the ceramic. Metallization of the ceramic, which is common in conventional soft or hard soldering, is not necessary with active soldering, as the solder, due to its chemical composition, forms a direct bond with the ceramic surface.
Implementation Method 2
the individual layers of the ceramic substrate are firmly bonded together by sintering
Data Source
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AI summary
A sensor comprises a preferably multilayered ceramic substrate (2) and at least one sensor element (1) arranged in, at or on the ceramic substrate (2). Contact can be made with the sensor element (1) via a metallic contact (6), wherein the metallic contact (6) is produced by means of a soldering connection that electrically connects the contact (6) to the sensor element (1) and in the process produces a fixed mechanical connection of the contact (6) relative to the ceramic substrate (2). A method for producing the sensor according to the invention is furthermore claimed.