Selective Electroplating Research Articles

Component reclamation and repair

Some further examples of reclamation and modification work carried out by selective electroplating and weld processing at Cookson Enterprises are detailed.

Laser surface modification for selective electroplating of metal: A 2.5 m/s laser direct write process

A very fast laser direct write process is described. The process involves laser modification of an insulating seed multilayer to form a conducting surface which can be electroplated. The seed layer is composed of an adhesion layer of TiW, a conducting layer of Au, and a top insulating layer of α-Si. The laser forms a Au-Si mixture without substantially affecting the adhesion layer. Writing speeds of 2.5 m/s have been demonstrated. The laser patterning can be performed in air, and the process works over a broad range of laser power (Pmax/Pmin ∼ 5).

A Fast Laser Alloying Process for the Selective Electroplating of Metal on SiO2 and Polyimide

AbstractA new laser direct-write process for patterning of metal on multichip modules has been developed. The process involves the laser modification of the non-conductive surface of a seed multilayer, converting it to a conductive surface, which can be electroplated with metal. The seed multilayer is composed of a TiW adhesion layer, onto which a Au film is sputtered, followed by an a-Si layer, which forms the non-conductive surface. The laser modifies the surface by alloying (or mixing) the Si and Au to form the conductive surface. This laser process has been shown to be capable of writing speeds of 2.5 m/s. With a silicon dioxide interlevel dielectric layer, the process works over a large range of laser power (Pmax/Pmin ∼ 5). A polyimide interlevel dielectric layer can be used without damage or loss of adhesion, although the process margin is substantially reduced (Pmax/Pmin ∼ 2).

High Speed Selective Electroplating with Impinging Two‐Dimensional Slot Jet Flow

The local mass‐transfer coefficient on a planar solid surface under an impinging two‐dimensional fluid jet was measured for both submerged and unsubmerged systems by an electrochemical technique. Correlations were developed for three regions along the surface: impingement, transition, and wall jet or lateral flow regions. For unsubmerged jets, a theoretical model of the current and potential distribution was developed. It was found that hydrodynamic conditions exert a strong effect on performance at high current densities since flow influences mass transfer and also the shape of the free surface that confines the potential field. The capability of achieving selective reaction in the impingement region was found to improve with increased current density and flow rate. Dimensionless criteria for the upper limit of such improvements were established.

EQUIPMENT

Selective electroplating equipment. The Electroplating Products and Equipment Business Area of Degussa AG, Frankfurt am Main, Federal Republic of Germany, has begun to supply a new selective electroplating plant. Under a cooperation agreement with the Telmec company of Milan, Italy, this business area of Degussa, which is based in Schwäbisch Gmünd, Germany, has begun to market the Telmec SL 6 ‘Tab Plater’ all over the world, with the exception of Italy and France. The equipment was developed specially for manufacturers of printed circuit boards, and is used for the continuous electroplating of strip contacts on these boards.

New products

The Electroplating Products and Equipment Business Area of Degussa AG, Frankfurt am Main, Federal Republic of Germany, has begun to supply a new selective electroplating plant. Under a co‐operation agreement with the Telmec company of Milan, Italy, this business area of Degussa, which is based in Schwäbisch Gmüd, Germany, has begun to market the Telmec SL 6 ‘Tab Plater’ throughout the world, with the exception of Italy and France. The equipment was developed specially for manufacturers of printed circuit boards, and is used for the continuous electroplating of strip contacts on these boards.

New Low Cost Substrate (Duroid) for Hybrid Microwave Integrated Circuits (MICs) in Wide Band

Because of its lower dielectric constant and loss tangent, and its greater surface smoothness, fused silica is very suitable for use in the KU band and above, but its cost is very high. The purpose of this paper is therefore to select a new substrate which competes with fused silica on the grounds of lower cost; to adapt the hybrid technology to this new substrate; to show ,comparing the measured performances of a filter realised on fused silica and on this new substrate, that the latter is suitable for MICs in the wide band, but not in the narrow band; and to describe an application of this substrate in the 22–24 GHz band. Thus, after an investigation of the electrical parameters and of the costs of different substrates, Duroid was selected and compared with silica. This substrate is composed of a non‐woven glass microfibre reinforced by polytetrafluorethylene; its microwave quality is theoretically almost similar to that of the fused silica one but its cost is much lower. The adaptation of hybrid technology on this substrate, notably in order to use beam lead and die semiconductor components with thermocompression bonding as a connection method, involved the use of a copper foil laminated on Duroid. This paper describes the process that has been perfected: selective electroplating of gold on copper, compatibility of etching solutions of gold and copper, attachment and connection methods of semiconductors, substrate attachment in a package, etc. A comparison of the performances of a filter realised on fused silica and on Duroid gives the following conclusion: Duroid is suitable for wide band circuits, but not for narrow band circuits because of its instability under stress test temperatures (−20 to 80°). In this last case, silica will be preferred. A transmitter‐receiver in the 22–24 GHz band for radio links is described.

On selective electroplating of gold in fabrication of MICs: S. Ahmad, M. Mustafa and J. Akhtar Microelectron. Reliab. 21 (5), 727 (1981)

On selective electroplating of gold in fabrication of MICs: S. Ahmad, M. Mustafa and J. Akhtar Microelectron. Reliab. 21 (5), 727 (1981)

High‐Speed Selective Electroplating with Single Circular Jets

High‐speed selective electroplating of circular deposits with a jet system was investigated by both experimental and theoretical studies. Direct measurement of current distribution was made with a sectioned electrode made of concentric rings. Three systems were studied, including alkaline ferricyanide reduction, copper deposition from acidified sulfate solution, and copper deposition from an acidified sulfate solution that also contained a ferric/ferrous redox couple. In these systems, current distribution data were obtained upon controlled variation of jet Reynolds number, electrolyte conductivity, reactant concentration, and applied total current. A mathematical model of the process was developed that included mass transfer, ohmic resistance, charge transfer, cell geometry, and multiple electrode reactions. The mathematical model was used to generate dimensionless contour maps indicating generalized conditions under which selective high‐speed electroplating can be accomplished.

On selective electroplating of gold in fabrication of MIC's

On selective electroplating of gold in fabrication of MIC's

On selective electroplating of gold in fabrication of MIC's

The analysis of the reasons causing degradation observed in resist layer during selective gold plating on patterns for MIC's has resulted in an excellent combination of electrolytic bath and photoresist type. Thick layers of gold (i.e. more than 10 μm) have been deposited by the method presented here over a period of about 1 h without any deterioration in the photoresist property. This combination can be used in the fabrication of beam lead devices with better results.

Thick photoresist patterns for selective electroplating

Photoresist patterns with a thickness of 2 μm–16 μm are often applied in selective electroplating processes. We will treat some problems concerning the generation of such thick photoresist patterns and especially discuss the obtainable accuracy and edge definition of these patterns. We have investigated several positive photoresists which have been deposited by spraying or roller coating. The obtainable accuracy has been established with the aid of a test pattern. Gap widening and strip narrowing are dependent on u.v. exposure time and developing time; both relationships have been investigated. Postbaking of some kinds of photoresist is necessary, because the patterns must be suitable for selective electroplating. Deviations of the patterns due to postbaking are also discussed. Before dealing with the photolithographic procedures, we will briefly discuss some properties of positive photoresists.

Thick photoresist patterns for selective electroplating : J. J. Maes, A. G. van Nie and G. B. A. Hut. Microelectron. Reliab.17, 325 (1978)

Thick photoresist patterns for selective electroplating : J. J. Maes, A. G. van Nie and G. B. A. Hut. Microelectron. Reliab.17, 325 (1978)