Optical Triggering for Solder Sphere Reflow in Hard Disk Drive Interconnects
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Solution Overview
Problem
The existing methods for connecting components in hard disk drives using solder material face challenges in precise positioning and processing, leading to undesirable heat transfer and potential damage to components due to high thermal energy application.
Innovation Solution
The method involves using optical detection to locate a solder sphere as it falls through a capillary and triggering a laser to melt and reflow the solder only when it reaches a predetermined position, minimizing contact with the capillary and allowing for accurate solder connections without excessive heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single high intensity laser pulse is applied to provide both melting and reflow energy, then the solder connection is formed, but excessive heat is conducted into the capillary wall and causes localized heat transfer to the slider
Solution Approach 1:
The single high intensity laser pulse is divided into two separate pulses: a first lower intensity pulse for initial melting and a second higher intensity pulse for reflow. This segmentation allows thermal energy to be applied in controlled stages, preventing excessive heat conduction to the capillary wall and reducing localized heat transfer to the slider while still achieving satisfactory solder connections.
2Reliability
If the solder sphere is heated to far greater than melt temperature for reflow, then the solder connection is achieved, but undesirable localized heat transfers to the slider or other components
Solution Approach 1:
The first laser pulse performs preliminary melting of the solder sphere before it contacts the bonding pads. This preliminary action ensures the solder is sufficiently molten for connection while the second pulse only provides additional reflow energy as needed, preventing excessive temperature elevation that would cause undesirable localized heat transfer to the slider or other components.
Solution Approach 2:
The laser heating is applied periodically in two distinct pulses rather than continuously. The first pulse melts the solder, the solder is deposited, then the second pulse provides reflow energy. This periodic application allows thermal management between pulses, preventing excessive heat accumulation and localized heat transfer to sensitive components.
3Manufacturing precision
If the solder sphere contacts the inner portion of the capillary, then the solder is contained and positioned, but heat is conducted into the capillary wall
Solution Approach 1:
The first laser pulse melts the solder sphere while it is still inside the capillary, performing the melting action before the solder contacts the capillary walls. This preliminary melting reduces the need for the solder to adhere to and remain in contact with the capillary inner portion, thereby reducing thermal energy conduction to the capillary wall while maintaining precise solder positioning.
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 enables precise and accurate solder connections with reduced heat transfer to components, improving the yield and longevity of the thermal interconnect process in high-density applications.
Implementation Method 1
applying a first laser through the capillary tube while measuring light from the first laser that reflects off the connection area as the solder sphere moves through the capillary tube
Implementation Method 2
applying a second laser to at least partially melt the solder sphere when the measured light decreases to a predetermined level and as the solder sphere falls from the exit orifice toward the connection area
Implementation Method 3
The use of such a single high intensity pulse results in the total thermal energy put into the solder sphere occurring in a relatively short time period
Data Source
AI summary
A method for interconnecting multiple components of an electrical assembly with a solder joint, including the steps of positioning a first component adjacent to a second component to provide a connection area, dispensing a solid solder sphere to a capillary tube, wherein the capillary tube is positioned with an exit orifice above the connection area between the first and second components, applying a first laser through the capillary tube while measuring light from the first laser that reflects off the connection area as the solder sphere moves through the capillary tube, and applying a second laser to at least partially melt the solder sphere when the measured light decreases to a predetermined level and as the solder sphere falls from the exit orifice toward the connection area between the first and second components.