Peter Torben Tang

Electroplating and characterization of cobalt-nickel-iron and nickel-iron for magnetic microsystems applications

The magnetic properties of pulse reverse (PR) electroplated CoNiFe and DC electroplated NiFe are presented. CoNiFe is a very promising material for magnetic microsystems due to the possibility of achieving a high saturation flux density (Bs) and a low coercivity (Hc). A new bath formulation has been developed, which by means of PR electroplating makes it possible to deposit high Bs CoNiFe with a low residual stress level. The magnetic properties have been determined using a new simple measurement setup that allows for wafer level characterization. The results have been validated by comparison to measurements performed with a vibrating sample magnetometer (VSM).

Microfluidic magnetic separator using an array of soft magnetic elements

We present the design, fabrication, characterization, and demonstration of a new passive magnetic bead separator. The device operates in an effective state when magnetized by an external magnetic field of only 50mT, which is available from a tabletop electromagnet. We demonstrate the complete capture of 1.0μm fluorescent magnetic beads from a 7.5μL sample volume traveling at an average linear fluid velocity of 5mm∕s.

Pulse reversal plating of nickel and nickel alloys for microgalvanics

Abstract The use of pulse reversal (PR) plating, as an alternative to the use of additives for electrochemical deposition of nickel, is studied. With optimised pulse plating parameters, and in some cases in combination with additives, substantial improvement of the deposit properties can be achieved. Utilising chloride-type baths, PR plating of pure nickel (and harder nickel–cobalt alloys) have been used to fabricate tools for micro-injection moulding (Polymer Structures for μTas, EuroSensors, Copenhagen, 27–30 August, 2000) and micromechanical structures. Furthermore, preliminary results from pulse plating experiments with ternary magnetic alloys, comprising 50–60% Co, 25–35% Fe and 10–20% Ni, will be reported. For both pure nickel and nickel alloys good chemically stable electrolytes have been developed, and the deposits are smooth with low residual stress. None of the electrolytes contain sulphur co-depositing additives (such as saccharin) nor wetting agents.

Methods for electrodepositing composition-modulated alloys

Abstract Materials exhibiting unique mechanical, physical and chemical properties can be obtained by combining thin layers of different metals or alloys forming a multilayered structure. Two general techniques exist for electrodepositing composition-modulated alloy (CMA) materials; dual-bath and single-bath plating. For both techniques a number of variation exist. The most suitable technique and variation for the manufacture of a certain CMA material is highly dependent on the metals included in the given CMA system and on the dimensions of the multilayered structure. In this paper, the main principles of the two electrochemical techniques and their variants are discussed.

Molybdate based passivation of zinc

SummaryIn order to reduce corrosion rates, zinc plated parts are usually chromated. Recently Chromates have caused increasingly environmental concern, for both allergic effects among workers touching chromated parts and toxic effects on fish, plants and bacteria.A molybdate based alternative has been developed to replace Chromates in several passivation applications. Depending on the environment in which the passivated parts are to be exposed, the protection that this alternative treatment provides range from less efficient to more efficient as compared to Chromate.These aspects as well as issues such as; cost, stability, layer composition and test results from several different corrosion tests are discussed.

Indirect tooling based on micromilling, electroforming and selective etching

Abstract The tool inserts used for injection moulding or hot-embossing of polymer micro-components, are the most important and expensive and crucial part of this important mass-production process. In this paper a new fabrication scheme is introduce, consisting of a combination of micro-milling, electroforming and selective etching. The basic concept is to exploit the benefit of true 3D-machining in a soft substrate such as aluminium with the excellent replication capabilities of nickel electroforming. The term indirect machining covers the fact that the master that is produced by machining a positive structure, i.e. the opposite of what is needed for the actual mould insert.

Pulse reversal plating of nickel-cobalt alloys

Abstract Electroforming, as a versatile process for fabrication of durable tools, is experiencing an increasing interest with the start of commercial use of products with micro or nanofeatures. Electroformed tools can be utilised for polymer, glass and metal replication processes and, in addition, when extreme demands, in terms of tool accuracy, process temperature and tool wear, are requested. In order to meet these demands, electroforming of hard nickel alloys is an obvious way forward. This paper presents several electrolytes from which it is possible to deposit nickel–cobalt alloys with high hardness (>550 HV), low internal stress and easy maintenance. Moreover, different organic complexing agents – as well as alternatives to boric acid – have been investigated.

Pulse Reversal PermAlloy Plating Process for MEMS Applications

Nickel-iron, and especially Permalloy, plating has been known and used for more than 40 years, but there are still several problems related to stability and maintenance that should be resolved. This paper presents a saccharine-free pulse reversal plating Permalloy electrolyte, which gives low-stress deposits. We demonstrate selected MEMS applications of the electrolyte. The use of the strong complexing agent 5-sulfosalicylic acid allows for a photometric determination of the Fe 3+ -level in the bath and eliminate precipitates. This makes the electrolyte suitable as a Permalloy plating process used on an irregular basis.

Process Chains and Tooling Concepts

This chapter is focused on micro-tooling and associated process chains. It gives definition of tooling and process chain first, followed by introducing tooling concepts, material compatibility, tooling techniques, such as direct and indirect tooling, etc. Criteria for the selection of tooling process chains are also recommended. Finally, two application cases are presented: molds for polymeric micro-fluidics and die/mold fabrication for micro-bulk forming.