Gold Bond Pads for Disk Drive Microactuator Grounding

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Solution Overview

Problem

Existing disk drive suspension technologies face challenges in creating low resistance electrical connections between stainless steel components and microactuators like PZT devices due to the chromium-rich passivation layer on stainless steel, which increases resistance with temperature, humidity, and time, and the mechanical strain induced by PZT displacement, rendering soft materials like solder inadequate.

Innovation Solution

Chemically activating the stainless steel surface and selectively plating it with gold to create gold bond pads, which provide a low resistance interface for bonding microactuators, using an elastomeric plating mask and electroplating high purity gold to ensure a durable and reliable ground connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If silver epoxy is used as conductive adhesive between mount plate and components, then electrical connection is achieved, but resistance increases with temperature, humidity, and time

Engineering Contradiction:

Improveelectrical connection stabilityVSAvoidresistance increase due to environmental factors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the material parameter from silver epoxy to gold plating, which fundamentally alters the electrical resistance characteristics. Gold plating provides stable, low resistance electrical connection that does not degrade with temperature, humidity, or time, directly resolving the reliability issue caused by environmental sensitivity of silver epoxy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies gold plating only in specific localized areas where electrical connections are needed, rather than covering the entire mount plate. This selective area approach reduces material usage and cost while maintaining the reliable electrical connection properties where required.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If soft materials such as solder are used for PZT/mount plate connection, then electrical connection is achieved, but connection fails under cyclic mechanical strain loads

Engineering Contradiction:

Improveelectrical connection durabilityVSAvoidmechanical strength under cyclic strain

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite interface structure by plating gold on the stainless steel mount plate surface. This gold layer combines the electrical conductivity needed for signal transmission with the mechanical strength required to withstand cyclic strain from PZT actuation, eliminating the failure mode of soft solder materials.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies gold plating specifically at the PZT/mount plate interface areas where both electrical connection and mechanical strength are critical. This localized treatment provides enhanced properties exactly where needed without affecting the overall suspension structure.

Inventive Principle:

Principle #3Local quality

3Reliability

If chromium-rich passivation layer is present on stainless steel surface, then corrosion resistance is improved, but electrical resistance increases

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidelectrical resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the mount plate surface into two functional zones: areas with chromium-rich passivation layer for corrosion protection, and areas with gold plating for low-resistance electrical connection. This segmentation allows both corrosion resistance and electrical conductivity to be optimized in their respective locations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gold layer acts as an intermediary between the stainless steel substrate and external electrical components. It provides a low-resistance electrical pathway while the underlying stainless steel with chromium passivation layer maintains corrosion resistance, mediating between electrical and protective functions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The gold bond pads significantly reduce surface resistance and withstand environmental degradation, maintaining a low resistance path even under cyclic loads and prolonged exposure to humid environments, as demonstrated by HAST testing, with results showing a dramatic improvement compared to prior art connections.

Implementation Method 1

The stainless steel surface is chemically activated to remove the chromium-rich passivation layer

Methodology Applied

Scientific EffectChemical activation: Chemical Bonding

Implementation Method 2

The chemically activated surface is then spot plated with gold (Au) to form gold bond pads

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS10876216B2Low resistance interface metal for disk drive suspension component grounding

Publication Date: 2020.12.29 MAGNECOMP CORP

AI summary

A stainless steel suspension component such as a mount plate is chemically activated by exposure to an activating solution. Gold is then spot plated onto the mount plate in the activated area using an elastomeric mask that is clamped over the mount plate. A component may then be bonded to the gold bond pads. The component may include a PZT microactuator bonded to the gold bond pads using a conductive adhesive such as silver epoxy. The gold acts as an interface metal that provides to a low resistance and environmentally robust ground path for the microactuator.