Laser Welded Microactuator Assembly for HDD Suspension
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Solution Overview
Problem
Conventional methods for bonding and connecting PZT microactuators to hard disk drive suspensions face issues such as depoling due to thermal mismatch and contamination from adhesives, and the time-consuming 'tail weave' process for wire connections.
Innovation Solution
A microactuator assembly using laser welding for mechanical and electrical connections, where PZT elements are bonded to stainless steel leads that can be welded directly to the suspension substrate, eliminating the need for high-temperature processes and adhesives, and allowing for separate fabrication and integration in a dirty environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive epoxy or high temperature adhesive is used to bond PZT to suspension substrate, then mechanical and electrical connection is achieved, but depoling occurs due to thermal mismatch and contamination is introduced
Solution Approach 1:
The patent extracts and eliminates the harmful adhesive bonding process entirely, replacing it with laser welding. This removes the source of depoling (high temperature thermal mismatch) and contamination (adhesive residues) while maintaining the mechanical and electrical connection function through direct metal-to-metal welding between stainless steel leads and the suspension substrate.
Solution Approach 2:
The patent replaces the chemical bonding mechanism (adhesive epoxy) with a thermal welding mechanism (laser welding). This substitution eliminates the harmful effects of adhesive curing temperatures and residues, achieving reliable electrical and mechanical connection through metallurgical bonding of stainless steel components without depoling the PZT.
2Strength
If high temperature processes are used for bonding and electrical connection, then strong mechanical bond is achieved, but PZT depoling occurs reducing displacement
Solution Approach 1:
The patent uses disposable stainless steel leads that are welded to the PZT and suspension substrate. These leads serve as both mechanical support and electrical connection, eliminating the need for high temperature adhesive curing. The welding process is localized and controlled, preventing thermal damage to the PZT while achieving strong mechanical and electrical bonds.
Solution Approach 2:
The patent changes the bonding temperature parameter from high temperature (adhesive curing at 100-200°C or higher) to low temperature (laser welding of thin stainless steel at controlled localized heat). This parameter change maintains bond strength while preventing PZT depoling and preserving displacement precision.
3Reliability
If tail weave process is used for wire connection to PZT, then electrical connection is achieved, but the process is time consuming and delicate
Solution Approach 1:
The patent merges the mechanical support function and electrical connection function into a single integrated stainless steel lead structure. The lead is welded directly to the PZT electrodes and extends to the suspension substrate, eliminating the separate tail weave process. This integration simplifies the assembly process, increases productivity, and maintains reliable electrical connection.
Solution Approach 2:
The stainless steel lead serves multiple functions simultaneously: it provides mechanical support for the PZT, conducts electrical signals to and from the PZT electrodes, and acts as a thermal path for laser welding. This multi-functionality eliminates the need for separate wire bonding operations, dramatically improving assembly speed while maintaining connection reliability.
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 maintains a higher percentage of original PZT displacement, reduces contamination risks, and eliminates the need for the 'tail weave' process, enhancing the efficiency and cleanliness of the assembly process while maintaining precise mechanical and electrical connections.
Implementation Method 1
A microactuator assembly containing a PZT is welded into place in a suspension and thus be both mechanically and electrically integrated into the suspension without any wires connected to the PZT element or the microactuator assembly
Data Source
AI summary
A microactuator assembly for a hard disk drive head suspension has an expandable base of stainless steel sheet material defining a negative lead affixed to the negative electrode on the bottom surface of a piezoelectric element, and a piece of stainless steel sheet material defining a positive lead attached to the positive electrode on the top surface of the piezoelectric element. The leads may be affixed directly to the piezoelectric element via conductive adhesive. The microactuator assembly can be assembled separately, and then laser welded into place on a suspension. A bond pad made of stainless steel sheet material extends from the flexible circuit, is electrically connected to the microactuator driving voltage conductor within the flexible circuit through a via, and is electrically isolated from the suspension substrate by an insulating film. The microactuator unit positive lead is mechanically and electrically connected to the bond pad via laser welding.