Graded Noble-Metal Lead Wire Coatings for Hermetic Feedthroughs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high cost of platinum and platinum/iridium lead wires in hermetic feedthrough assemblies for medical devices, combined with issues of poor oxidation resistance and adhesion in alternative materials, leads to manufacturing challenges and compromised performance.
Innovation Solution
A functionally graded noble metal-containing coating is applied to a non-noble metal wire core, providing a barrier against material diffusion and ensuring strong adhesion, thus enabling the use of lower-cost lead wires with biocompatibility and mechanical strength comparable to platinum/iridium wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum or platinum/iridium lead wires are used, then biocompatibility and mechanical strength are improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent uses a composite structure consisting of a non-noble metal core (such as tungsten, molybdenum, or tantalum) combined with a noble metal coating (such as platinum, palladium, or rhodium). This composite approach allows the lead wire to achieve the biocompatibility and corrosion resistance of noble metals while utilizing the mechanical strength and cost advantages of non-noble metal cores, thereby resolving the contradiction between reliability and manufacturing cost
Solution Approach 2:
The patent applies a thin noble metal coating (1-10 micrometers) only on the surface of the non-noble metal core, rather than using solid noble metal throughout. This local application of noble metal properties where they are most needed (at the surface for biocompatibility and corrosion resistance) while maintaining the structural integrity through the non-noble metal core significantly reduces material cost while preserving essential functionality
2Ease of manufacture
If mechanically clad coating is applied to non-noble metal wire core, then cost is reduced, but adhesion is poor causing brazing and welding problems
Solution Approach 1:
The patent specifies precise coating thickness parameters (1-10 micrometers) and uses thermal diffusion coating processes that allow controlled intermixing at the interface between the non-noble metal core and noble metal coating. This parameter control creates a gradient interface structure that enhances adhesion strength while maintaining the cost benefits of using non-noble metal cores, resolving the contradiction between manufacturing cost and adhesion reliability
3Ease of manufacture
If vacuum deposition coating is applied to non-noble metal wire core, then coating can be applied, but high stresses limit thickness to 2,000-5,000 nm
Solution Approach 1:
The patent replaces the vacuum deposition process with a thermal diffusion coating process. This substitution eliminates the high stress issues inherent in vacuum deposition that limit coating thickness, allowing the formation of thicker noble metal coatings (1-10 micrometers) on non-noble metal cores through a low-stress thermal diffusion mechanism that maintains coating integrity and adhesion
4Strength
If thin coating layer (100-1,000 nm) is applied to non-noble metal wire core, then stress forces are reduced, but coating is insufficient to prevent material migration to surface
Solution Approach 1:
The patent optimizes the coating thickness parameter to 1-10 micrometers, which is thicker than the 100-1,000 nm range that provides insufficient barrier function. This increased thickness, achieved through low-stress thermal diffusion processing, simultaneously provides adequate stress resistance while establishing an effective diffusion barrier that prevents non-noble metal atoms from migrating to the surface during brazing and welding operations
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 allows for the production of hermetic feedthroughs with non-noble metal lead wires at reduced costs while maintaining biocompatibility, mechanical strength, and hermeticity, preventing material erosion and ensuring reliable performance in medical devices.
Implementation Method 1
provides a functionally graded noble metal-containing coating on the non-noble metal wire core that acts as a barrier to migration of the non-noble metal to the surface of the wire
Implementation Method 2
A functionally graded noble metal-containing coating is applied to a non-noble metal wire core
Data Source
AI summary
A feedthrough filter capacitor assembly is described. The feedthrough filter capacitor assembly comprises an outer ferrule hermetically sealed to an insulator of a dielectric material seated within the ferrule. The insulative material is also hermetically sealed to at least one lead wire. Instead of being made of platinum or platinum/iridium, the lead wire comprises a core of a non-noble metal supporting a functionally graded coating. The metal core has an inner layer of the same the non-noble metal of the core and an outer layer of a noble metal. A gradient transition zone exists between the non-noble metal and the outer noble metal. Consequently, lead wires having all the beneficial attributes of platinum and platinum/iridium wire can be built into hermetic feedthroughs, but at a significantly reduced cost. In a preferred form, a filter capacitor is mounted on the insulator and electrically connected to the lead wires and to the ferrule to prevent unwanted EMI signals from traveling along the wires and entering the interior of the medical device.