Technical Paper: PIM International, Vol.2 No. 2 June 2008, pages 68-73, 2780 words

Authors: Carl Wu [1], Sundar V. Atre [1], Sachin Laddha [1], Shiwoo Lee [1], Kevin Simmons [2], Seong-Jin Park [3], Randall M. German [3] and Donald T. Whychell, Sr. [4]

[1] Oregon Nanoscience and Microtechnologies Institute, Oregon State University
106, Covell Hall, Corvallis, OR 97330, USA
[2] Pacific Northwest National Laboratory, Richland, WA 99354, USA
[3] Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, MS 39762, USA
[4] CM Furnaces, Bloomfield, NJ 07003, USA

Abstract

Microsystem technology has propelled the development of micro and multi-scale manufacturing techniques for more than a decade. Among these techniques, micro powder injection moulding (micro PIM) is drawing attention recently as one of the most cost-effective processes suitable for medium and mass production of micro components such as ceramic microchannel arrays. Fast mould filling during the fabrication can cause particles to migrate because of the increased shear rate in the cavity. This paper presents an in-depth study on the material homogeneity issue from micro PIM at both macroscale (short shot) and microscopic (binder/powder separation) levels. The study is based on newly developed experimental and simulation platforms which can be used as a development tool for micro PIM and microsystem designs. Key words: Ceramic microfabrication, powder injection moulding, microchannel arrays.

Introduction

A recent study panel sponsored by NSF, DOE, ONR and NIST-ATP analysed the emerging global trend towards developing new materials, manufacturing processes and metrology tools for the net-shape production of miniaturised, engineering components [1]. The panel reported on many exciting opportunities for miniaturised devices made of non-silicon materials, using non-lithographic manufacturing processes (Fig. 1). A significant finding of the panel was that in these micromanufacturing areas, research and education in the US were lagging well-behind Europe and Asia. The present paper is aimed at resolving these issues. It addresses the net-shaping of miniaturised components from metals and ceramics by powder injection moulding (PIM). PIM offers potential advantages in shape complexity, materials utilisation, energy efficiency, low-cost production, and mass manufacturing [2].
Microsystem technologies have strongly influenced the development of micro and multi-scale manufacturing techniques during the last decade. Recent breakthroughs in development include nanoscale powders, new binder systems, special micro injection tools, and new machines creating miniature parts with dimensions lt; 1 mm [3].

Further sections of this article include:

- Experimental Methods
- Part Design
- Materials
- Processing
- Characterisation
- Modeling
- Results and Discussion
- Optical microscopy
- Optical Surface Profilometry
- Image Analysis
- Nanoindentation
- Flow Simulations
- Conclusions
- Acknowledgement
- References

Figures and Tables:

Fig. 1 A microfluidic device made by PIM

Fig. 2 Schematic (Top) and injection moulded (Bottom) ceramic microchannel arrays (MCAs) used in this study

Fig. 3 Outline of overall approach.

Fig. 4 MCA parts for the present PIM study

Fig. 5 Schematic representation of the mould used in the present study. A view of the MCA cavities and runner system is also shown

Fig. 6 Top-view of a macroscale defect in the form of a short shot shown in a green MCA

Fig. 7 Side-view of a macroscale defect in the form of a short shot shown in a 50ìm MCA

Fig. 8 Side-view of a crack and possible powder-polymer separation in a 100ìm MCA

Fig. 9 Variation in rib height across the center of a green 50ìm MCA

Fig. 10 Variation in rib height across the center of a sintered 50ìm MCA

Fig. 11 Surface plot of rib height variation of green (top) and sintered (bottom) 50ìm MCA

Fig. 12 Grain and pore size variation near the top (left) and bottom (right) of a 50ìm rib

Fig. 13 Grain and pore size variation in ribs of 100ìm (left) and 500ìm (right) MCAs

Fig. 14 Particle distribution in ribs and bulk body of 50ìm and 500ìm sintered MCAs

Fig. 15 Sampling regions for XPS analysis in a green 50ìm MCA

Fig. 16 Variation in Al/C ratios along various locations in a green 50ìm MCA

Fig. 17 Variation in Al/C ratios of 50ìm MCAs from different process conditions

Fig. 18 Sampling regions for nanoindentation analysis in a green 50ìm MCA

Fig. 19 Variation in modulus along various locations in a green 50ìm MCA

Fig. 20 Variation in rib modulus of 50ìm MCAs from different process conditions

Fig. 21 Variation in cavity pressure from 0-30 MPa in a 50ìm MCA during mould filling of alumina-polyacetal feedstock

Fig. 22 Variation in cavity pressure from 0-3 MPa in a 50ìm MCA during mould filling of alumina-wax feedstock

Table 1 MCA dimensions, mm