Laser-Brazed Molybdenum Pin and Aluminum Lead Joint
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Solution Overview
Problem
Laser welding techniques face challenges in achieving consistent and robust weld joints, particularly when joining incompatible materials like aluminum and molybdenum, which often result in brittle welds due to mixing of metals.
Innovation Solution
A method involving laser brazing is developed to join molybdenum and aluminum pieces by forming a channel in the aluminum lead to house the molybdenum pin, where the aluminum is melted to create a strong, non-brittle joint with minimal mixing, using a laser brazing apparatus to align and secure the pieces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser welding is used to join aluminum and molybdenum pieces, then the pieces are heated to high temperature to melt and coalesce together, but the resulting weld joint is highly brittle due to mixing of the two metals
Solution Approach 1:
The invention introduces a filler metal layer that segments the direct contact between aluminum and molybdenum, preventing their mixing. The filler metal forms separate bonding interfaces: one with aluminum and another with molybdenum, thereby eliminating the brittle intermetallic compound layer that would form from direct aluminum-molybdenum contact.
Solution Approach 2:
The filler metal acts as an intermediary material between aluminum and molybdenum. It mediates the bonding process by forming a eutectic alloy with aluminum that has lower melting point, allowing the aluminum side to bond at lower temperatures while the molybdenum side bonds at higher temperatures, thus preventing direct mixing of aluminum and molybdenum.
2Manufacturing precision
If laser welding is used to join metals, then energy from the laser beam penetrates through the first metal piece into the second metal piece to heat and melt them, but obtaining consistent and robust weld joints is challenging due to geometry and material incompatibility
Solution Approach 1:
The invention changes the thermal parameters of the joining process by introducing a filler metal with eutectic composition. This allows the aluminum side to be processed at lower temperatures (around 580°C eutectic point) while the molybdenum side is processed at higher temperatures, creating optimal bonding conditions for each material without requiring extreme temperatures throughout the entire joint.
Solution Approach 2:
The filler metal layer is pre-applied to the aluminum surface before the laser welding process. This preliminary action ensures that when the laser beam is applied, the aluminum melts into the filler metal immediately, forming the eutectic alloy and preventing direct contact between aluminum and molybdenum, thus ensuring consistent joint quality.
3Length of moving object
If small diameter welds are required for electrochemical cell components, then the geometry of a round pin sitting on a flat lead creates challenges for qualification
Solution Approach 1:
The invention transitions from a point-contact geometry (round pin on flat lead) to a distributed bonding interface by applying filler metal that creates lateral bonding zones. The laser beam is applied from the side rather than from above, creating bonding in a different spatial dimension and ensuring adequate heat distribution and mixing across the joint area.
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 consistent and strong joint between molybdenum and aluminum, avoiding the formation of brittle intermetallics by ensuring only the aluminum is melted, thus relieving stress and maintaining a proper joint composition.
Implementation Method 1
energy from a laser beam penetrates through a first metal piece into a second metal piece, which accordingly heats portions of the two pieces to a sufficiently high temperature
Implementation Method 2
the second material of the lead is melted at the first joint to at least partially close the channel opening at the location of the first joint
Data Source
AI summary
In various examples, a component is for use in an implantable medical device. The component includes a pin including a first material attached to a lead including a second material different from the first material of the pin. At least a portion of the lead includes a channel in which at least a portion of the pin sits, the channel including a channel opening defined at least partially by opposing first and second channel sides extending a channel length. At least a first joint is formed along at least a portion of the first channel side. The first joint includes the second material of the lead deformed to at least partially close the channel opening to retain the pin within the channel to attach the lead to the pin. In some examples, the first material includes molybdenum and the second material includes aluminum.