DD286930A7 - METHOD FOR THE PRODUCTION OF MICROWIRED - Google Patents

Abstract

The invention relates to a method for producing high-purity micro-wire for the semiconductor industry. The object and the object of the invention are to produce micro-wires with a high surface quality and high circular symmetry with increased drawability, avoiding stress inconsistencies occurring inside the wire after high degrees of deformation and an increase in the yield strength, yield strength and elongation at break without exceeding a doping limit of the accompanying elements of 100 ppm * can be reached. This is achieved by performing composite deformation during cold drawing, whereby the logarithmic cold working degree f1 can not exceed 3.85 and a 25% drawing grading is to be used. The composite deformation is to be performed at a sheath / core wire diameter ratio of 2: 1 with a 20% die step. The minimum degree of deformation f2 in the composite, based on the core wire, is 3.98. The exposed core wire is further deformed step by step from a degree of deformation f34.61 to a degree of deformation f36.00 at drawing increments of 15% to 8% by cold drawing to final dimension of 0.03 mm and subsequently a continuous annealing with a flow rate of 4 m / s at 200 subjected to 750C.

Description

Field of application of the invention

The invention relates to a method for producing micro-wire from metals, preferably in the diameter range between 0.05 to 0.02 mm, for electrical conductors of electrical engineering and electronics and for the production of microthermal elements, resistors, microelectrodes and bonding wires.

Characteristic of the known technical solutions

Various methods are already known for the production of microwire jn up to a diameter of 0.001 mm. The most common method is the stepwise cold drawing of wires through increasingly narrow carbide or diamond dies in single or multiple passes (A.Galeji "The Calculation of Forces and Working Demands in Shaping in the Plastic State of Metals" - 2nd revised edition 1955, Akademieverlag Budapest).

The production of micro wires after the o.g. Drawing process requires a lot of equipment, tools and productive working time. The use of drawing diamonds of particularly high quality in small gradations and therefore large numbers, the 'possible low pulling speeds below 1 m / s, the necessary individual processing of each drawing stage and the abner nendem wire diameter occurring frequent Drahtrissc and small draw lengths of only a few hundred meters lead Overall, this represents a significant increase in the price of this type of production and thus limits production capacities. The cause of frequently occurring wire tears is due to the fact that, as is known, during cold drawing the material is forced in the radial direction to a different voltage, the Botrag of the degree of deformation, the drawing angle, the friction value and the surface distance is dependent. It is also known that in cubic-surface-centered metals after cold drawing a double fiber texture of the type (100) and (111) occurs and the proportions of boids textures vary greatly both in the axial and in the radial direction, as well as the texture sharpness. As a result of the inhomogeneous state of tension and texture, very high localized stress peaks in micro-regions occur at high degrees of deformation, which are far greater than the applied external tensile stress. As a result, the material in these micro-areas is overstressed and leads to said unwanted wire cracks. With decreasing specific strength on the one hand and reduced diameter of the wires on the other hand, technical possibilities as they are introduced when pulling stronger wires or those with higher specific strength properties must be omitted, since the decreasing absolute tensile loads of the wires require the use of high degrees of deformation or multiple deformation steps no longer allow an operation. To overcome these difficulties, the Wollastone process has been developed and further improved by the solutions disclosed in DRP 286717 and US Patent 3505039.

According to these solutions, the wire to be formed is surrounded by a much thicker concentric sheathing of silver and deformed in the composite to final diameter and then removed the silver sheath mechanically or chemically with nitric acid.

Using these methods, the pulling cost is reduced back to the level practiced for thicker wires, i. H. Multiple drawing machines with larger graduations can be used. The drawability is significantly improved by pulling speed of several m / s and wire lengths of several thousand meters. Nachte'lo this method, however, consist in that the surface of Wollastondrähten compared to the surface of cold drawn wires infoige strong Riefigkeit has significantly deteriorated and their wire cross-section deviates significantly from the circular shape. Furthermore, during the etching process due to the chemically induced release time for the removal of the silver shell, the throughput speeds are so low that the previously eingesp, rto effort in the drawing process is largely compensated again by the high temporal Atzaufwand.

The production of micro-wires according to the Direktziehverfahren and the Wollastonverfahren is thus possible only with considerable technical and economic effort. They do not make it possible to realize economy, high surface quality and wire roundness in one process.

Object of the invention

The object of the method according to the invention is to economically produce micro-steels of Au, AuAg, AISi ₁ , AgPd and other metals with high surface quality, high circular symmetry and improved mechanical properties with increased drawability.

Explanation of the essence of the invention

Central technical goal of the present invention is to avoid the stress inhomogeneities in the interior of the wire occurring after high degrees of deformation and to increase the yield strength ratio, the yield strength and the elongation at break, without exceeding a doping limit of the accompanying elements of 100 ppm by mass.

According to the invention, the object is achieved in that, within a cold deformation, a composite deformation with correspondingly matched parameters between degree of cold deformation φ] before the jacket, shell thickness to core wire diameter, degree of expansion in the composite q> ₂ . Verbundzieh- and subsequent cold drawing technology is inserted, wherein the logarithmischo Cold Forming Cp ₁ before the mantle must be <3.85 in a Ziehsallestufung s 25%. For the intermeshed composite deformation with a sheath core wire diameter ratio of 2: 1, a minimum core wire deformation of q> 2 to 3.98 with a maximum cross-sectional reduction of s20% occurs when using any lubricant. The total strain amount to shell removal with respect to the core wire must be (J) ₁ -; a 7.83.

In the subsequent cold drawing operation to <p ₃ £ Ί, 61, die increments of s are 15%, νοηφ ₃ > 4.61 to cp ₃ £ 5.23, die increments of -S 10%, and φ ₃ > 5.23 to ^ ₃ = 6, 00, apply increments of <8% when using any lubricant. After the deformation to final gauge, a continuous annealing is carried out with an annealing speed S4m / s at eider temperature of 200 ° C to 75O ⁰ C.

As metallic Mantelwerks toffe preferably 99.9% strength electrolyte copper or electrolyte silver are used.

embodiment

The invention Suü _.i a. Embodiment will be explained in more detail.

99.99% or 99.999% gold studs are pressed cold from 25 mm to 6 mm diameter using conventional presses. From 6mm to 3.65mm, corresponding to a logarithmic cold working degree of φ = 0.99, the diameter is reduced in a single straight draw with drawing increments of 15 to 20%.

Gold wire prepared in this way is cleaned with tetra and placed in an electrolyte copper tube measuring 8 × 2 mm, previously treated with a solution consisting of 25 to 70% by volume of acetic acid, γ = 1.05, 20 to 60% by volume of nitric acid , γ = 1.54.0 to 30Vol .-% water and 0 to 500g / l copper salts and 1 ml / l silicone oil at a temperature of 20 ° C to 3O ⁰ C, threaded threaded.

Subsequently, a deformation of the composite wire in the straight-pull up to 3.65 mm with drawing increments of 15 to 20%.

From 3.65mm diameter to 0.85mm diameter, a 15% die coulter is used before finally forming in the multiple draw a deformation up to 0.2mm composite diameter with 15% grading.

The electrolytic copper f / antel is then chemically removed with nitric acid to provide a 0.1 mm diameter gold wire.

Dio deformation in a multiple pulley from 0.1 to 0.03 mm in diameter is carried out in three stages in a multiple pulley with the following grading steps:

0.1-0.0 mm Diameter: 10% 0.0485-Ό, 0367 mm Diameter: 9% 0.0367-0.030mm Diameter: 5%.

The drawing speed is 3m / s, as a lubricant, dielectric is used.

According to the requirements, a poor condition is set by a final annealing in a continuous process at temperatures of.! 00 ⁰ C bif, 600 ° C.

The invention is characterized by a variety of advantages compared to the prior art. The high degree of cold deformation produces a high surface quality and circularity of the cross section.Dio achievable wire lengths of several thousand meters enable economical wire production and allow subsequent technological processes such as annealing, cleaning The formation of damaging local stress peaks is prevented, the formation of a displacement and texture structure favorable for the cold forming takes place, and by increasing the proportion of the <111) texture, a substantial improvement in the mechanical properties takes place, in that the breaking elongation, the yield strength and yield ratio are increased while increasing the tensile strength.

The wire produced by the proposed method has such properties as are indispensable for use on automatic bonding machines, namely diameter tolerance £ 0.001mm, surface roughness <0.0005mm, increased yield ratio> 0.9.

Claims (2)

1. A process for the production of microwire by a step-by-step drawing process in conjunction with a composite deformation and a final annealing process, characterized in that the blank first drawn to a degree of deformation φ, rS3.85 with a drawing grading ^ 25%, then a composite deformation at a diameter ratio sheath / core wire 2: 2: 1, a degree of deformation φ ₂ > 3.98, based on the core wire, and a Ziehsteinabstufung <20% is performed and after removal of the sheath of the core wire in three stages Forming degree φ ₃ to 4,61 with drawing scale <15% Forming degree φ ₃ from 4.61 to 5.23 with drawing step <10% forming step <p ₃ from 5.23 to 6.00 with drawing step <8% drawn to the final dimension and then in passing at a speed <4 m / s at 200 ⁰ C to 75O ⁰ C is annealed. 2. The method according to item 1, characterized in that for the composite deformation, a metallic sheath of electrolyte-copper or electrolyte-silver is grown on the core wire.