Chapter 6: LIGA and Micromolding

Introduction

LIGA—Background

History

Synchrotron Orbital Radiation (SOR)

Introduction

Technical Aspects

Access to the Technology

LIGA and LIGA-Like Process Steps

X-Ray Masks

Introduction

X-Ray Membrane (Mask Blank)

Absorber Materials

Absorber Fabrication

Single Layer Absorbers

Stepped Absorber

CNC Machined Absorbers

Alignment of X-Ray Mask to Substrate

Conformal, Transfer, or Self-Aligned Mask for High-Aspect-Ratio Microlithography

Choice of Primary Substrate

Resist Requirements

Methods of Resist Application

Multiple Spin Coats

Commercial PMMA Sheets

Casting of PMMA

Resist Adhesion

Stress-Induced Cracks in PMMA

Exposure

Optimum Wavelength

Deposited Dose

Stepped and Slanted Microstructures

Development

Comparison of Master Micromold Fabrication Methods

Metal Deposition

Introduction

Electroless Metal Deposition

Introduction

Electroless Plating in the IC Industry and in Micromachining

Contacts and connectors

Cabinets and enclosures

Auxiliary equipment used in device fabrication

Active Elements

Chip carriers and packages

Measuring Thickness of Plated Layers

Electrodeposition

Introduction

Electroplating

Diffusion-Limited Reactions

Nonlinear Diffusion Effects on Microelectrodes

Finishing Metal Parts and Metal Mold Inserts

Nickel Electrodeposition

Physical Properties of Electrodeposited Nickel

Pulse Plating of Ni

Copper Electroplating

Copper in Printed Circuit Boards

Copper in ICs—The Damascene Process

Thin Film Inductive Magnetic Heads

Gold Electroplating

Other Plating Applications

Plating Automation

Plating Issues

Conclusions on Electroless and Electroplating through Polymer Masks

Molding

Introduction

Liquid Resin Molding Techniques

Introduction

Reaction Injection Molding (RIM) and Transfer Molding

LIGA and LIGA-Like Applications of RIM

Casting

Summary: Pros and Cons of RIM

Injection Molding (IM)

Introduction

Conventional Injection Molding

Injection Compression Molding

Thin-Wall Injection Molding

Summary: Pros and Cons of IM

Compression Molding

Introduction

Hot Embossing

Summary: Pros and cons of compression molding

Demolding

Introduction

Demolding in LIGA and LIGA-Like Applications

Sacrificial Layers

Alternative Materials in LIGA

Examples

6.1 Electromagnetic Micro Motor

6.2 LIGA Spinneret Nozzles

6.3 LIGA Fiber-Chip Coupling

Problems