Feedthrough Pin Notching for Implantable Pulse Generator Welding
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Solution Overview
Problem
Conventional implantable pulse generators face challenges in securely and reliably connecting wire conductors to feedthrough structures, leading to potential disconnections and damage due to differences in thermal diffusivity and reflectivity between materials like platinum and MP35N, which complicates laser welding processes.
Innovation Solution
The method involves laser machining feedthrough pins to create notches, using a combination of platinum and gold with ceramic, and employing adaptations like dimples and tabs to shield wires from direct laser exposure, ensuring a robust electrical connection by conducting heat and managing strand separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to connect wire conductors to feedthrough structures, then electrical connections can be established, but wire pulling away and disconnection occur due to differences in thermal diffusivity and reflectivity between materials
Solution Approach 1:
A specialized welding component is introduced as an intermediary between the wire conductor and the feedthrough pin. This component includes a cup portion that receives the wire and a flange portion that interfaces with the feedthrough pin, creating a transition zone that manages the thermal and mechanical stresses during laser welding. The intermediary component prevents direct welding between dissimilar materials (platinum wire to MP35N pin), thereby eliminating the wire pulling away problem caused by differential thermal expansion and reflectivity mismatches.
Solution Approach 2:
The welding component is designed with specific geometric parameters including a cup portion with controlled depth and diameter, and a flange portion with specific thickness and outer diameter. These parameter optimizations ensure proper wire containment within the cup and adequate heat dissipation, while the flange provides sufficient surface area for reliable laser welding to the feedthrough pin. The parameters are tuned to manage thermal diffusivity differences between materials.
2Ease of manufacture
If conventional welding methods are used without protective features, then welding operations can be performed, but wire strands separate and connection quality deteriorates
Solution Approach 1:
The cup portion of the welding component is designed to pre-position and contain the wire conductor before the laser welding operation begins. The cup geometry (depth and diameter ratios) is optimized to hold the wire strands together and prevent them from splaying or separating during the welding process. This preliminary mechanical constraint ensures that when laser energy is applied, the wire remains properly aligned and bundled, maintaining connection quality without requiring complex welding controls.
3Productivity
If direct laser exposure is applied to wire-conductor interfaces, then welding can proceed, but thermal damage and strand separation occur
Solution Approach 1:
The welding component creates localized quality variations in the welding zone. The cup portion concentrates and distributes laser energy locally around the wire-conductor interface, while the flange portion provides a larger surface area for heat dissipation. This local quality control ensures that the wire strands receive sufficient heat for welding without excessive thermal input that would cause strand separation or material degradation. The geometry optimizes the local thermal field to protect sensitive wire structures.
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 approach enhances the manufacturing yield by preventing wire pulling away during welding, ensuring a secure and reliable bond between conductors and feedthrough pins, thereby improving the durability and reliability of the electrical connections within the implantable pulse generator.
Implementation Method 1
laser machining each of the plurality of feedthrough pins to comprise a notch along a surface of the respective feedthrough pin
Implementation Method 2
performing welding operations to connect the plurality of conductors of the lead body with the plurality of feedthrough pins of the feedthrough component
Implementation Method 3
ensuring a robust electrical connection by conducting heat and managing strand separation
Data Source
AI summary
In one embodiment, a method of fabricating an implantable pulse generator, comprises: providing a lead body including a plurality of conductors; providing a feedthrough component comprising a plurality of feedthrough pins; hermetically enclosing pulse generating circuitry and switching circuitry within a housing, the feedthrough component being welded to the housing; laser machining each of the plurality of feedthrough pins to comprise a slot along a surface of the respective feedthrough pin; placing a respective conductor from the lead body in the respective slot of each of the plurality of feedthrough pins; and performing welding operations to connect the plurality of conductors of the lead body with the plurality of feedthrough pins of the feedthrough component.