Wrap-Around Electrode Microactuators for Wafer-Level Bonding
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Solution Overview
Problem
The existing methods for bonding piezoelectric elements (PZTs) to suspension components in hard disk drives are time-consuming, costly, and prone to contamination due to the use of liquid adhesives, with challenges in controlling adhesive flow and requiring multiple curing steps.
Innovation Solution
The use of adhesive films and wrap-around electrodes simplifies the assembly process by integrating adhesives at the wafer level and reducing the number of curing steps, along with B-staging techniques to control adhesive flow and eliminate contamination sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid adhesives are used to bond PZTs to suspension components, then bonding strength is achieved, but contamination risk increases and process complexity increases due to multiple curing steps
Solution Approach 1:
The patent extracts the adhesive application process from the final assembly stage and relocates it to the wafer fabrication stage. Adhesive patterns are printed directly on the PZT wafer before dicing, eliminating the need for liquid adhesive dispensing in the cleanroom assembly environment. This removes the contamination source while maintaining bonding strength through controlled adhesive application.
Solution Approach 2:
The adhesive is applied and partially cured (B-staged) on the PZT wafer before the PZT is mounted to the suspension. This preliminary action allows the adhesive to be in a controlled, semi-cured state that prevents excessive flow during assembly while still providing adequate bonding. The final curing occurs after assembly, completing the bonding process without requiring multiple curing steps during assembly.
2Reliability
If multiple curing steps are used to ensure complete adhesive bonding, then bonding reliability is improved, but manufacturing time and process complexity increase
Solution Approach 1:
The adhesive is B-staged (partially cured) on the wafer before assembly, which prevents excessive flow during mounting. This single preliminary curing step replaces multiple curing steps, as the adhesive completes its cure after assembly rather than requiring intermediate curing cycles. This reduces manufacturing time while maintaining bonding reliability through the controlled B-staging process.
3Manufacturing precision
If adhesive flow is allowed to occur during assembly, then complete coverage is achieved, but control over adhesive thickness and placement is lost
Solution Approach 1:
The adhesive is printed in precise patterns on the PZT wafer and B-staged before assembly. This preliminary application with controlled thickness eliminates the need for adhesive flow during assembly to achieve coverage. The B-staging prevents excessive flow while the printed pattern ensures complete coverage of required areas, maintaining both precision and ease of manufacture.
Solution Approach 2:
The adhesive is B-staged by controlling the degree of cure to achieve a specific viscosity state that prevents flow during assembly. This parameter change from liquid to semi-cured state allows the adhesive to be applied with precise thickness control while maintaining ease of application through the printed pattern approach.
4Reliability
If conventional electrode configurations are used on PZTs, then electrical connections are established, but assembly complexity increases due to multiple connection points
Solution Approach 1:
The patent merges the electrical connection function into the adhesive bonding process by incorporating conductive adhesive or conductive elements in the adhesive pattern. This combines the mechanical bonding and electrical connection functions into a single step, reducing assembly complexity while maintaining connection reliability. The wrap-around electrode configuration further simplifies connections by allowing both drive and ground connections to be made from one face of the PZT.
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 process efficiency, reduces costs, and improves repeatability and predictability by controlling adhesive thickness and eliminating the need for multiple curing steps and liquid adhesives in the assembly environment.
Implementation Method 1
A piezoelectric element or component, made of piezoelectric material, sometimes referred to simply as a PZT, is often used as the microactuator motor
Implementation Method 2
The use of adhesive films and wrap-around electrodes simplifies the assembly process by integrating adhesives at the wafer level
Data Source
AI summary
A method of manufacturing a piezoelectric microactuator having a wrap-around electrode includes forming a piezoelectric element having a large central electrode on a top face, and having a wrap-around electrode that includes the bottom face, two opposing ends of the device, and two opposing end portions of the top face. The device is then cut through the middle, separating the device into two separate piezoelectric microactuators each having a wrap-around electrode.