Implantable Device Header Welding Heat Management
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Solution Overview
Problem
Current methods for assembling implantable medical devices, such as cardiac pacemakers, are complex, time-consuming, and prone to tolerance issues and heat damage during welding, which can lead to unreliable connections and potential leakage in hermetically sealed housings.
Innovation Solution
A pre-fabricated header and hermetically sealed housing with metal fastener parts that allow for a metal-to-metal welded joint at a distance from the housing, reducing heat exposure and tolerance problems, and enabling easy inspection and assembly with large tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the header is welded directly to the housing, then a strong connection is achieved, but severe heat development occurs that may melt the polymeric material and damage the conductor arrangements
Solution Approach 1:
The invention divides the welding process into two separate stages: first welding the header to the support plate (both polymeric components), then welding the support plate to the housing (metal component). This segmentation prevents excessive heat buildup that would occur in direct header-to-housing welding, as the support plate acts as a thermal buffer between the welding zones.
Solution Approach 2:
The support plate serves as an intermediary component between the header and the housing. It provides a metal mounting surface for the header while maintaining electrical insulation from the housing, and its metallic structure allows it to withstand welding heat without transferring excessive heat to the polymeric header, thus protecting the conductor arrangements.
2Ease of manufacture
If the header is pre-molded with through going holes and locked by cross pins, then assembly is simplified, but only very small tolerances are acceptable and the mounting operation becomes complicated
Solution Approach 1:
The invention changes the geometric parameters of the support plate, specifically providing it with an extended surface that protrudes from the housing. This extended surface creates a larger welding area and allows for greater positioning tolerances during assembly, eliminating the need for very small tolerances required by cross-pin locking mechanisms.
3Reliability
If welding is performed carefully to avoid heat damage, then the polymeric material and conductor arrangements are protected, but the welding operation becomes time consuming and complex
Solution Approach 1:
The support plate is pre-positioned on the housing with its extended surface protruding outward before the header is attached. This preliminary arrangement allows the header to be welded to the support plate first (away from the housing), and then the support plate is welded to the housing. This sequence of preliminary actions protects the header from heat damage while maintaining efficient welding operations.
4Strength
If a metal support plate is used to retain the header, then a strong mechanical connection is achieved, but the welding operation may cause severe heat development
Solution Approach 1:
The welding process is segmented into two separate operations: welding the header to the support plate, and welding the support plate to the housing. This segmentation allows the heat-affected zones to be separated in space and time, preventing the cumulative heat buildup that would occur in a single direct welding operation, while still achieving strong mechanical connections at both interfaces.
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 provides a strong, reliable, and easy-to-inspect connection between the header and housing, minimizing heat damage and tolerance issues, while allowing for efficient assembly and leak testing, thus enhancing the durability and reliability of the medical device.
Implementation Method 1
the housing fastener part and the header fastener part are connected by a connecting weld at a distance from the housing
Data Source
AI summary
In an implantable medical device and a method for assembly thereof, a hermetically sealed housing encloses electronic circuitry and has a housing fastener part that is formed of metal and that protrudes from the housing. A per-fabricated header, for receiving conducting leads and for connecting the conducting leads to the electronic circuitry, has a header fastener part also formed of metal. The header is fastened to the housing by metal-to-metal welding of the housing fastener part and the header fastener part at a distance from the housing.