TWI587317B - Corrosion and moisture resistant bonding wire - Google Patents

Description

Corrosion and moisture resistance bonding wire

The present invention relates to a wire comprising a copper core having a thickness of from 8 μm to 80 μm, the copper core comprising: copper; nickel in an amount of from 0.005 wt.-% (weight-%, weight%) to 5 wt.-% In the range; and optionally, the amount of silver is in the range from 0.005 wt.-% to 1 wt.-%, wherein all amounts in wt.-% are based on the total weight of the core; wherein the copper core has It is in the average grain size in the range from 1.5 μm to 30 μm. The invention further relates to a procedure for making such a line.

The use of bonding wires in electronic applications and microelectronic applications is well known in the art. Although the bonding wire is made of gold at the beginning, less expensive materials such as copper are used today. Although copper wire provides very good electrical and thermal conductivity, copper wire bonding is still challenging. In addition, copper wires are susceptible to corrosion and oxidation.

In terms of line geometry, the most common are those having a circular cross section and a joint strip having a generally rectangular cross section. Both types of line geometry have the advantage of making them useful for a particular application.

Some of the latest developments involve bonding wires with copper cores. As the core material, copper is selected for high conductivity. Different dopants of the copper material have been sought to optimize the bonding properties. For example, US 7,952,028 B2 describes several different copper-based test lines with a large number of different dopants and concentrations.

However, in terms of the bonding wire itself and the bonding process, there is a continuing need to further improve the bonding wire technology.

Accordingly, it is an object of the present invention to provide improved bonding wires.

Another object of the present invention is to provide a bond wire that exhibits excellent bondability in terms of stitch bonding.

Another object of the present invention is to provide a bond wire having improved reliability and improved corrosion resistance and moisture resistance.

Another object of the present invention is to provide a bond wire that exhibits improved reliability and bondability in terms of ball bonding.

Another object of the present invention is to provide a bond line that exhibits improved roundness and concentricity of the joined ball in terms of ball wedge engagement.

It has been found that the wire of the present invention addresses at least the goal of improving corrosion resistance and moisture resistance. In addition, procedures have been found for manufacturing such lines.

The subject matter of the category forming request item contributes to the solution of the above objectives. The sub-claims of the category forming request represent representative embodiments of the present invention, and the subject matter of the sub-claims also facilitates solving the above-mentioned objectives.

A first aspect of the invention is a wire comprising a core comprising or consisting of (a) nickel in an amount from 0.005 wt.-% to 5 wt.-%, preferably 0.1 wt. .-% to 0.6 wt.-% or even 0.45 wt.-% to 0.55 wt.-%, (b) as the case may be, silver, the amount is from 0.005 wt.-% to 1 wt.-%, Preferably, in the range of 0.1 wt.-% to 0.6 wt.-% or even 0.45 wt.-% to 0.55 wt.-%, (c) copper, in an amount ranging from 94 wt.-% to 99.98 wt.-%, Preferably in the range of 98.5 wt.-% to 99.6 wt.-% or even 99.4 wt.-% to 99.6 wt.-%, and (d) 0 wt.-ppm to 100 wt.-ppm (weight-ppm, weight ppm) The other components, wherein all amounts in wt.-% and wt.-ppm are based on the total weight of the core, wherein the core has an average grain size in the range from 1.5 μm to 30 μm, the average size Determined according to the line interception method, Wherein the line has an average diameter in the range from 8 μm to 80 μm or even 12 μm to 55 μm.

The wire is preferably used for bonding wires in a microelectronic device. The line is preferably an integral item. A wide variety of shapes suitable for use in the present invention are known and appear. In the cross-sectional view, the preferred shape is a circular shape, an elliptical shape, and a rectangular shape.

The average diameter is obtained by the "size measurement method". According to this method, the physical weight of the line of defined length is determined. Based on this weight, the diameter of the wire (the density of copper: ρ _Cu = 8.92 g/cm ³ ) was used to calculate the diameter of the wire. The average diameter is calculated as the arithmetic mean of the five measurements obtained when five lines are cut.

For the purposes of the present invention, the term "joining line" includes both the cross-section of all shapes and all common line diameters, but a bonding line having a circular cross-section and a fine diameter is preferred.

The line intercept method used to determine the average grain size is a standard metallographic practice. Here, the line is cut perpendicular to the direction of the line, and the resulting profile is etched. In the context of the present invention, the size of the grains is defined as the longest of all profiles through the straight line of the grains. The average grain size is the arithmetic mean of at least seven grain measurements in the core/block material. The test was performed in accordance with ASTM E112-96 (Chapter 16.3, page 13).

As already mentioned, the core comprises (a) 0.005 wt.-% to 5 wt.-% nickel and (c) 94 wt.-% to 99.98 wt.-% copper. The core may or may not comprise component (b), ie silver. If the core comprises silver, the amount of silver is in the range from 0.005 wt.-% to 1 wt.-%.

The core of the present invention comprises (d) from 0 wt.-ppm to 100 wt.-ppm of other components. The low amount of these other components ensures good reproducibility of the nature of the wire. In the context of the present invention, these other components (often also referred to as "inevitable impurities") are derived from trace amounts of chemical elements and/or compounds present in or derived from the raw materials of the wire manufacturing process. Examples of such other components are: Mn, Pt, Cr, Ca, Ce, Mg, La, Al, B, Zr, Ti, S, Fe.

In other words, the core comprises or consists of the following (a) nickel in an amount ranging from 0.005 wt.-% to 5 wt.-%, preferably 0.1 wt.-% to 0.6 wt.-% or even 0.45 wt.-% to 0.55 wt.-%, (b) silver in an amount ranging from 0.005 wt.-% to 1 wt.-%, preferably 0.1 wt.-% to 0.6 wt.-% or even 0.45 wt.-% to 0.55 wt.-%, (c) copper in an amount ranging from 94 wt.-% to 99.98 wt.-%, preferably 98.5 wt.-% to 99.6 wt.-% or even 99.4 wt.-% to 99.6 wt.-%, And (d) 0 wt.-ppm to 100 wt.-ppm of other components, or (a) nickel, the amount of which is from 0.005 wt.-% to 5 wt.-%, preferably 0.1 wt.-% to 0.6 wt. -% or even in the range of 0.45 wt.-% to 0.55 wt.-%, (b) no silver, (c) copper, the amount of which is from 94 wt.-% to 99.98 wt.-%, preferably 98.5 wt. -% to 99.6 wt.-% or even 99.4 wt.-% to 99.6 wt.-%, and (d) 0 wt.-ppm to 100 wt.-ppm of other components, wherein wt.-% and All amounts in wt.-ppm are based on the total weight of the core.

In accordance with the above, embodiments of the present invention are a line comprising: (a) nickel, (b) optionally, silver; and (c) copper, as disclosed above. Other components present in the core are typically not added separately. The presence of other components is derived from impurities present in one or more of nickel, silver and copper.

In one embodiment, the core of the present invention comprises less than the following other components: (i) Mn, <15 wt.-ppm; (ii) Pt, Cr, Ca, Ce, Mg, La, Al, Any of B, Zr, and Ti, each of which is <2 wt.-ppm; (iii) any of S and Fe, each of which is <10 wt.-ppm.

Preferably, the material forming the core satisfies at least two of the above limits, and the material forming the core preferably satisfies all of the limits.

In one embodiment, the core comprises elemental phosphorus as a dopant, the amount being in the range of from 40 wt.-ppm to 80 wt.-ppm, based on the total weight of the core.

In the context of the present invention, a core is defined as a homogeneous region of bulk material. Since any bulk material always has a surface area that exhibits different properties to some extent, the nature of the core is understood to be the nature of the homogeneous region of the bulk material. The surface of the bulk material region may vary in morphology, composition (e.g., oxygen content), and other characteristics. The surface can be attached to the outer surface of the core. In the alternative, it can tie the interfacial region between the core and the coating superimposed on the core.

In the context of the present invention, the term "overlay" is used to describe the relative position of a first item (e.g., a copper core) relative to a second item (e.g., a coating). "Overlay" characterization, other items (such as the middle layer) may be (but need not be) configured between the first item and the second item. Preferably, with respect to the total surface of the first item, the second item is at least partially superimposed on the first item, such as at least 30%, 50%, 70% or at least 90%. Optimally, the second item is completely superimposed on the first item.

In the context of the present invention, the term "intermediate layer" refers to the area of the line between the core and the coating. In this region, there is a combination of materials for both the core and the coating.

In the context of the present invention, the term "thickness" is used to define the size of the layer in a direction perpendicular to the longitudinal axis of the core, the layer being at least partially superposed on the surface of the core.

In one embodiment, the ratio between the core diameter and the average grain size is in the range from 2 to 14 or even 2 to 7.

In one embodiment, the average diameter of the wires is in the range of from 15 μm to 28 μm. In this case, the average grain size in the core is preferably in the range of from 1.5 μm to 6 μm.

In another embodiment, the average diameter of the wires is in the range from >28 [mu]m to 38 [mu]m. In this case, the average grain size in the core is preferably in the range of from 2 μm to 10 μm.

In another embodiment, the average diameter of the wires is in the range from >38 [mu]m to 50 [mu]m. In this case, the average grain size in the core is preferably in the range of from 5 μm to 15 μm.

In another embodiment, the average diameter of the core is in the range from >50 [mu]m to 80 [mu]m. In this case, the average grain size in the core is preferably in the range of from 7 μm to 30 μm.

In an embodiment, the core has a surface, wherein the coating is superposed on the surface of the core.

In one embodiment, the mass of the coating is no greater than 2.5 wt.-%, preferably no greater than 2 wt.-% or less, relative to the total mass of the core. When a coating is present, it often has a minimum mass of 0.1 wt.-% or greater or 0.5 wt.-% or greater relative to the total mass of the core. The use of a low amount of material as a coating preserves the properties defined by the material of the core. On the other hand, the coating imparts specific characteristics to the surface of the wire, such as inertness to the environment, corrosion resistance, improved bondability, and the like. For example, for a line having an average diameter of 18 μm, the thickness of the coating is in the range from 60 nm to 70 nm. For example, for a line having an average diameter of 25 μm, the coating may have a thickness in the range from 90 nm to 100 nm.

In one embodiment, the coating is made of an element selected from the group consisting of palladium, platinum, and silver. The coating can be a single layer of one of the elements. In another embodiment, the coating can be a plurality of layers of overlapping adjacent layers, each layer being made of an element selected from the group consisting of palladium, platinum, and silver. Each layer that is part of the coating is deposited separately from one of the above pure metal elements. Common techniques for depositing such elements on a core are plating (such as electroplating and electroless plating), self-vapor deposition materials (such as sputtering, ion plating, vacuum evaporation, and physical vapor deposition) and Melt deposition material.

In one embodiment, another coating is superposed on the coating. In one embodiment, the mass of the other coating is no greater than 0.2 wt.-%, preferably no greater than 0.1 wt.-%, relative to the total mass of the core.

For example, for a line having an average diameter of 18 μm, the thickness of the other coating It is in the range from 2 nm to 4 nm. For example, for a line having an average diameter of 25 μm, the other coating may have a thickness from 3.5 nm to 5.5 nm.

In an embodiment, the other coating is a gold layer.

In an embodiment, the line of the invention is characterized by at least one of the following features:

α) Corrosion resistance has a value of at most 0% of the bonded ball peeling; see "Test Method G" as described below.

β) Moisture resistance has a value of at most 0% of the bonded ball peeling; see "Test Method I" as described below.

The hardness of the γ) core is not more than 120 HV, preferably not more than 115 HV or not more than 110 HV; see "Test Method J" as described below.

δ) The stitching of the program window area has a minimum of 40μm. g or at least 90μm. g or at least 120μm. The value of g, each value is provided before the line has an average diameter of 18 μm; see the section "Test Method C" as described below.

The resistivity of the ε) line is not more than 1.80μΩ. Cm.

ζ) The average bonded ball roundness has a value of at most 0.0025 μm or at most 0.002 μm or at most 0.0018 μm, each value being provided before the line has an average diameter of 18 μm; see the section "Test Method E" as described below "."

η) The average joined ball concentricity has a value of at most 0.00056 μm or at most 0.0005 μm or at most 0.0004 μm, each value being provided before the line has an average diameter of 18 μm; see the section "Test Method E" as described below "."

A second aspect of the invention is a program for making a line in any of the above disclosed embodiments. In its most general embodiment, the program includes at least the following program steps

(1) Providing a precursor item comprising or consisting of: (a) nickel in an amount of from 0.005 wt.-% to 5 wt.-%, preferably 0.1 wt.-% to 0.6 wt. .-% or even in the range of 0.45 wt.-% to 0.55 wt.-%, (b) optionally, the amount of silver is from 0.005 wt.-% to 1 wt.-%, preferably 0.1 wt.-% to 0.6 wt.-% or even 0.45 wt.-% to 0.55 wt.-% In the range, (c) copper, in an amount ranging from 94 wt.-% to 99.98 wt.-%, preferably 98.5 wt.-% to 99.6 wt.-% or even 99.4 wt.-% to 99.6 wt.-% And (d) 0 wt.-ppm to 100 wt.-ppm of other components, wherein all amounts in wt.-% and wt.-ppm are based on the total weight of the precursor item, (2) The precursor item is elongated to form a line precursor until the desired diameter of the core is obtained; and (3) the elongated line precursor obtained after completion of the procedure step (2) is annealed.

The precursor item as provided in step (1) of the procedure can be obtained by alloying and/or doping copper with a desired amount of nickel and optionally silver. Alloying and doping are achieved by creating a melt of the components and copper and cooling the melt to form a copper-based homogenous precursor term. Typically, such precursor items are in the form of rods having a diameter of, for example, 2 mm to 25 mm and a length of, for example, 5 m to 100 m. Such a rod may be made by casting a copper alloy melt comprising or consisting of the following in a suitable mold having room temperature, followed by cooling and solidification: (a) nickel in an amount From the range of 0.005 wt.-% to 5 wt.-%, (b) depending on the case, silver, the amount is in the range from 0.005 wt.-% to 1 wt.-%, (c) copper, the amount is in self Other components in the range of 94 wt.-% to 99.98 wt.-%, and (d) 0 wt.-ppm to 100 wt.-ppm, wherein all amounts in wt.-% and wt.-ppm are based on copper The total weight of the alloy melt. The copper alloy itself can be prepared by conventional procedures known to those skilled in the art of metal alloys, for example, by melting together copper, nickel, and optionally silver at a desired ratio. In this way, conventional copper-nickel and copper-silver master alloys can be utilized. For example, an induction furnace can be used to perform the melting procedure, and it is advantageous to operate under vacuum or under an inert gas atmosphere. The materials used may have a purity level of, for example, 99.99 wt.-% and higher.

If one or more coatings are present on the wire as disclosed in certain embodiments of the first aspect of the invention, then such coatings are preferably applied to the wire precursor. Familiar with this item The skilled person knows how to calculate the thickness of such coatings on the precursor item by the thickness disclosed for the line embodiment (ie, after elongating the precursor item with one or more coatings into a line precursor). These coatings are obtained. As disclosed above, numerous techniques for forming coatings of materials on the surface of copper or copper alloys in accordance with such embodiments are known. Preferred techniques are plating (such as electroplating and electroless plating), deposition of materials in the vapor phase (such as sputtering, ion plating, vacuum evaporation, and physical vapor deposition) and deposition of molten materials.

As disclosed in certain embodiments of the first aspect of the invention, in order to stack a single or multiple layers of metal coating to the core, once a precursor diameter in the range of, for example, 80 μm to 200 μm is reached It is advantageous to interrupt the program step (2). The single or multiple layer metal coating can then be applied, for example, by one or more plating procedure steps. Thereafter, the program step (2) is continued until the desired and final diameter of the core is obtained.

In process step (2), the precursor item is elongated to form a line precursor until the desired diameter of the core is obtained. Numerous techniques are known for elongating precursor items to form line precursors and appear to be useful in the context of the present invention. The preferred technique is rolling, swaging, die drawing, etc., wherein die pulling is particularly preferred. In the latter case, the precursor item is drawn in several procedural steps until the desired and final diameter of the core is reached.

The desired and final diameter of the core may be in the range of from 8 μm to 80 μm or preferably in the range of from 12 μm to 55 μm. Such wire drawing processes are well known to those skilled in the art.

Conventional tungsten carbide and diamond die can be used, and conventional drawn lubricant can be used to support drawing. For example, the precursor items can be drawn in 8 major stages, and each stage has 15 to 25 program steps, wherein in each drawing procedure step, the length of the precursor item is extended from 6% to 18% range. The elongation % may be the same or different for each drawing procedure step.

In the process step (3), the elongated wire precursor obtained after the completion of the process step (2) is preferably annealed in a tube furnace. Preferably, the annealed strand is annealed (final annealing), which is A continuous program for allowing rapid production lines with high reproducibility. Strand annealing means that the wire precursor is annealed in a dynamic manner while moving through a preferred tube annealing furnace and wound onto a reel after exiting the furnace. The annealing is performed at a target temperature in the range of, for example, 440 ° C to 700 ° C for 0.1 second to 0.4 seconds, preferably at a target temperature in the range of 470 ° C to 650 ° C for 0.1 second to 0.3 seconds; The /time condition allows the average grain size of the core to be achieved or adjusted.

Annealing is typically performed by pulling an elongated wire precursor through a conventional annealing furnace, typically in the form of a cylindrical tube of a given length and having a defined temperature profile at a given annealing speed. The given annealing speed can be selected, for example, from 4 meters/minute to 30 meters/minute or from 14 meters/minute to 16 meters/minute. In this way, the annealing time/target temperature parameter can be defined and set.

With respect to embodiments of the present invention, it has been discovered that annealing at temperatures below the maximum elongation temperature can produce beneficial line properties because the line morphology can be affected in a positive manner. Furthermore, it has been found that it is further advantageous to select the annealing temperature above the maximum elongation temperature while maintaining the annealing time constant. For example, this manufacturing principle can be used to adjust the average grain size of the line to, for example, a larger average grain size. By this adjustment, other properties such as line hardness, ball bonding behavior, and the like can be affected in a positive manner.

Thus, in one embodiment, the annealing is performed at a temperature above the maximum elongation temperature, wherein the elongation value of the wire after annealing is no greater than 98% of the maximum elongation value. For example, the program step (3) can be performed at a temperature at least 10 ° C higher than the maximum elongation temperature T _{ΔL (max)} , preferably at least 50 ° C higher, or at least 80 ° C higher. Generally, the temperature in the procedure step (3) is not higher than T _{ΔL(max) by} more than 200 °C. The maximum elongation temperature T _ΔL(max) is determined by the elongation at break of the test sample (line) at different temperatures. Data points were collected in a graph showing the elongation (%) as a function of temperature (°C). The resulting graph is often referred to as the "annealing curve." In the case of a copper-based wire, the temperature at which the elongation (%) reaches the maximum value is observed. This is the maximum elongation temperature T _ΔL(max) . An example is shown in Figure 1, which shows an exemplary annealing profile of a 18 [mu]m copper wire alloyed with nickel according to Sample 3 (Table 1). The annealing temperature is a variable parameter of the x-axis. The graph shows the measured values of the line breaking load (BL, gram) and elongation (EL, %). The elongation was judged by a tensile test. In the example shown, the elongation measurement exhibited a typical local maximum of about 10%, which was achieved at an annealing temperature of about 470 °C. If the line according to sample 3 is not annealed at this maximum elongation temperature but at 560 ° C (which is 90 ° C higher than the maximum elongation temperature), the result is an elongation value of about 9.8%, which is greater than the maximum elongation. The value is 2% lower.

The annealing can be performed in an inert or reducing atmosphere. Numerous types of inert atmospheres and reducing atmospheres are known in the art and are used in sweeping annealing furnaces, which are typically tubular annealing furnaces. Nitrogen is preferred in known inert atmospheres. Hydrogen is preferred in known reducing atmospheres. Another preferred reducing atmosphere is a mixture of hydrogen and nitrogen. Preferably, the hydrogen-nitrogen mixture is from 90 vol.-% to 98 vol.-% nitrogen and thus from 2 vol.-% to 10 vol.-% hydrogen, wherein the total vol.-% is 100 vol.-%. Preferably, the nitrogen/hydrogen mixture is equal to 93/7, 95/5 and 97/3 vol.-%/vol.-%, each based on the total volume of the mixture. It is especially preferred to apply a reducing atmosphere during annealing if portions of the wire surface are susceptible to oxidation by oxygen in the air (e.g., if the copper of the wire is exposed to its surface). In such type of an inert gas or a reducing gas to be cleaned is preferred to 43min ^-1 125min ^-1, more preferably 43min ^-1 to 75min ^-1, the optimal range of 50min ^-1 to 63min ^-1 in the gas exchange rate (=Gas flow rate [L/min]: Inner furnace volume [L]) is executed.

It is believed that the unique combination of the composition of the precursor item material (which is identical to the composition of the finished core) and the program parameters prevailing during the procedure step (3) is essential to obtaining the line of the present invention. One of the program parameters is preferably a combination of a target temperature of 500 ° C to 650 ° C for 0.1 second to 0.3 seconds, preferably further combined with 90 vol.-% to 98 vol.-% nitrogen / 2 vol.-% to 10 vol.- % of hydrogen as a sweep gas mixture, the gas exchange rate to be in the range of 50min ^-1 to 63min ^-1 in the.

After the completion of the procedure step (3), the line of the present invention is completed. In order to fully The nature benefits, and it is advantageous to use the line immediately for wire bonding applications (i.e., without delay, for example, no more than 7 days after the completion of program step (3)). Alternatively, in order to maintain the wide line of the wire in conjunction with the nature of the program window and to prevent it from being oxidized or otherwise chemically attacked, typically immediately after completion of program step (3) (ie, without delay, for example, at the completion of the program step ( 3) The finished wire is wound and vacuum sealed after <1 hour to 5 hours and then stored for further use as a bonding wire. Storage under vacuum tight conditions should not exceed 6 months. After the vacuum seal is turned on, the wire should be used for wire bonding for no more than 7 days.

Preferably, all of the process steps (1) through (3) and the winding and vacuum sealing are performed under clean room conditions (US FED STD 209E cleanroom standard, 1k standard).

A third aspect of the invention is a line obtainable by a procedure according to the second aspect of the invention or its embodiment. This wire has been found to be very suitable for use as a bond wire in wire bonding applications. Wire bonding techniques are well known to those skilled in the art. During the wire bonding process, a ball joint (first joint) and a stitch joint (second joint, wedge joint) are usually formed. During the formation of the joint, a specific force (usually measured in grams) is applied with the aid of the applied scrubbing amplitude (usually measured in units of μm). The arithmetic product of the difference between the upper and lower limits of the applied force in the online bonding procedure and the difference between the lower and lower limits of the applied scrubbing amplitude defines the line bonding program window: (the upper limit of the applied force - the lower limit of the applied force). (Upper limit of applied scrubbing amplitude - lower limit of applied scrubbing amplitude) = wire bonding program window.

The wire bond program window definition allows for the formation of areas of force/scouring amplitude combinations that meet the specifications (ie, by custom tests such as conventional tensile tests, ball shear tests, and ball pull tests, just to name a few).

For industrial applications, it is desirable to have a wide wire bond window (force in g versus scrub range in μm) for reasons of line bonding robustness. The wire of the present invention exhibits a relatively wide line of joint programming windows. For example, for stitch bonding, the line of 18 μm in diameter of the present invention exhibits a wire bonding procedure in the range of, for example, 40 μm to 120 μm. window.

The following non-limiting examples illustrate the invention.

Instance

Test method A. to J.

All tests and measurements were performed at T = 20 ° C and relative humidity RH = 50%.

A. The average grain size is obtained by the line intercept method:

The grain size was determined using standard metallographic techniques (ASTM E112-96, Chapter 16.3, page 13). The sample of the core is cut and then etched. In the case of the present invention, etching was carried out using a solution of 2 g of FeCl ₃ and 6 ml of concentrated HCl in 200 ml of deionized water. The grain size is determined according to the line interception principle. In the context of the present invention, the size of the grains is defined as the longest of all profiles through the straight line of the grains. The measured average grain size is the arithmetic mean of at least seven measurements of the grains in the core material.

B. Elongation (EL):

The tensile properties of the wire were tested using an Instron-5300 instrument. The line was tested at a speed of 1 inch per minute over a 10 inch gauge length. The load and elongation at break (break) were obtained according to ASTM standard F219-96. Elongation The difference between the length of the tether line before and after the tensile test (ΔL/L), which is calculated from the extended tensile profile based on the recorded load.

C. Pin-type joint program window area:

The measurement of the bonding program window area is performed by a standard procedure. The test lines were joined using a KNS-iConn adapter tool (Kulicke & Soffa Industries Inc, Fort Washington, PA, USA). The second joint (pin stitch) program window area is the product of the difference between the upper and lower limits of the force used in the joint and the difference between the upper and lower limits of the applied scrub range, wherein the resulting joint must meet certain tensile test specifications, For example, the pulling force of 2.5 grams, the non-stick on the lead, and the like. The program window value is based on a line having an average diameter of 18 μm, wherein the lead fingers to which the wires are bonded are composed of silver.

The four corners of the program window are derived by overcoming the following two main failure modes: (1) supply too low force and scrubbing amplitude will result in non-stick on the wire lead (NSOL), and (2) supply too high force and The scrub level will result in a short tail (SHTL).

D. Free Air Ball (FAB):

The FAB is evaluated by performing an conventional electric torch (EFO) ignition in two different modes: (a) standard ignition - single step, and (b) advanced ignition - two steps, see the table below:

The table is based on the procedure described in the Free Air Ball KNS Program User Guide (Kursofarmer Industries, Fort Washington, Pennsylvania, USA, May 31, 2009). The FAB diameter was measured at a magnification of 200X to 500X using an optical microscope on a μm scale. Scanning electron microscopy (SEM) was used to observe the morphology of FAB. The shape and symmetry of the molten droplets of the wire material suspended at the wire ends prior to stitch bonding were evaluated.

Assessment of the effectiveness of the FAB configuration:

+, the line melt droplets solidify, but the ball size is smaller than the gauge and / or tip

++, the wire melt droplets solidify in the shape of a sphere, but the size of the sphere does not conform to the specification and/or is inclined

+++, the wire melt droplets solidify in the shape of a sphere and within the specification, but slightly tilted

++++, the wire melt droplets solidify in a spherical and axisymmetric spherical shape.

E. Average joint ball roundness and concentricity:

The joined sphere (first joint) morphology is quantified by measuring the average circularity and concentricity. The wires are joined using a standard ignition mode or an advanced ignition mode. The 4N bare copper and nickel alloyed copper wires are joined using a standard ignition mode, while the silver-nickel alloyed copper wires are joined using an advanced ignition mode.

The conjugated spheres were observed at a magnification of 500X in a high magnification Nikon microscope MM40. The e-max software version 5.3 interconnected with the microscope predicts the theoretical circle by the least squares method for the 16 measured edge points. Find the deviation of each edge from the theoretical circle radius. The difference between the maximum deviation value and the minimum deviation value is defined as DevE, which is the average circularity of the joined balls. Balls with good roundness exhibited an average circularity of 0.001 μm and a poorer spherical exhibiting an average circularity of 0.003 μm.

In the case of an average joined ball concentricity, 12 edges are marked along the outer circle. The e-max software predicts the theoretical circle by the least squares method and finds the center of the outer circle. Similarly, it predicts the inner circle and its center. Calculate the center difference between the outer circle and the inner circle in both the X direction and the Y direction, according to which the center difference is To calculate concentricity. The bonded balls with good concentricity exhibited 0.0001 μm, and the worst shot exhibited 0.0009 μm.

F. Soaking test for salt solution of continuous casting rod:

A continuously cast 8 mm rod of length 10 mm was dispensed and immersed in a salt solution for 4 days at 85 ° C, rinsed with DI water and later rinsed with acetone. The salt solution contained 20 wt.-% NaCl dissolved in deionized (DI) water. The surface discoloration of the rods was observed at a magnification of 10X to 100X under a low magnification mirror (stereoscopic-SZX16). The transition from the original copper red to the dark black rod surface indicates corrosion at several locations. The SEM-EDX on the dark black surface reveals the peaks of chlorine, oxygen and copper.

Evaluation:

+, 100% of the cast rod surface changed from the original copper red to dark black, indicating a number of crevice corrosion

++, <70% cast rod surface changed from original copper red to black, indicating crevice corrosion

+++, <40% cast rod surface changed from original copper red to black, indicating slight crevice corrosion

++++, <10% cast rod surface changed from original copper red to dark black, indicating that crevice corrosion is less significant or non-existent

G. Soaking test on the salt solution of the bonded ball:

The ball was bonded to an Al-0.5 wt.-% Cu bond pad. The test device with the wire thus joined was immersed in the salt solution at 25 ° C for 2, 4, 6, 8 and 10 minutes, rinsed with DI water and later rinsed with acetone. The salt solution contained 30 wt.-ppm NaCl dissolved in deionized (DI) water. The number of peeled balls was examined at a magnification of 10X to 100X under a lower magnification mirror (stereoscopic mirror-SZX16). A higher number of peeled balls were observed to indicate some interface galvanic corrosion.

H. Test for moisture resistance of continuous casting rods:

A continuously cast 8 mm rod of 10 mm length was dispensed and stored in a highly accelerated stress test (HAST) chamber at 130 ° C temperature, 85% relative humidity (RH) for 4 days. The HAST test samples were examined at a magnification of 10X to 100X under a low magnification mirror (stereoscopic-SZX16) to see surface discoloration. Similar to the salt solution soak test, the change from the original copper red to the dark black rod surface indicates corrosion at several locations. The SEM-EDX on the dark black surface reveals oxygen peaks and copper peaks.

Evaluation:

+, 100% of the cast rod surface changed from the original copper red to dark black, indicating a number of crevice corrosion

++, <70% cast rod surface changed from original copper red to black, indicating crevice corrosion

+++, <40% cast rod surface changed from original copper red to black, indicating slight crevice corrosion

++++, <10% cast rod surface changed from original copper red to dark black, indicating that crevice corrosion is less significant or non-existent

I. Test for moisture resistance of bonded balls:

The ball was bonded to an Al-0.5 wt.-% Cu bond pad. The test device with such a bonded wire was stored in a highly accelerated stress test (HAST) chamber at 130 ° C temperature, 85% relative humidity (RH) for 20 hours, and later at a lower magnification mirror (stereoscopic mirror) -SZX16) The number of peeled balls is checked at a magnification of 10X to 100X. A higher number of peeled balls were observed to indicate some interface galvanic corrosion.

J. Vickers hardness:

The hardness was measured using a Fischer mirror H110C test apparatus with a Vickers indenter. A force of 10 mN was applied to the test line sample for a residence time of 5 s. This test is performed on the center of the annealed core.

Example 1-10

A certain amount of at least 99.99% pure copper material ("4N copper") is melted in the crucible. A small amount of the master alloy is added to the copper melt and the uniform distribution of the added components is determined by stirring. The following master alloys were used.

For the alloys of Tables 1 and 2, a corresponding combination of the parent alloys Cu-5wt.-%Ni, Cu-15wt.-%Ag, and Cu-0.5wt.-%P was added. Then, a wire precursor in the form of a rod of 8 mm was continuously cast from the melt.

The 8 mm rods were drawn in 6 main draw stages (22 program steps in each stage) to form a line of circular shape with an average diameter of 18 μm, wherein the precursors were self-executed in each of the program steps. 6% to 18% of the length is elongated. In the examples presented herein, 17% elongation was practiced for stage 1, 11% elongation was practiced for stage 2 to stage 5, and 8% elongation was practiced for stage 6. A slip agent is used during drawing.

By means of this procedure, samples of copper-nickel and copper-nickel-silver alloy wires and a comparative wire (Ref) were produced.

The chemical composition of copper, copper-nickel and copper-nickel-silver alloy wires was controlled by ICP (inductively coupled plasma) analysis using a Perkin Elmer ICP-OES 7100DV model. The line was dissolved in concentrated nitric acid and the solution was used for ICP analysis.

Table 1 shows groups 1 to 6 of the inventive copper-nickel alloy wire having an average diameter of 18 μm. to make. The nickel content of the line changes as indicated, and the amount of phosphorus also changes as indicated. The comparative line (Ref) consists of 4N copper.

Table 2 shows the composition of sample lines 7 to 10 each having an average diameter of 18 μm. The silver, nickel and phosphorus contents of the lines vary as indicated. The comparative line (Ref) consists of 4N copper.

The wires are annealed in the final annealing step. The annealing is performed as a strand annealing by passing the wires at a speed of 1 m/s through a tube annealing furnace having a length of 30 cm and an annealing temperature of 560 ° C (line 1-6) or 650 ° C (line 7-10). It is executed dynamically. After exiting the furnace, the wires are wound onto a reel for packaging.

In the example of the present invention, the annealing time is a given moving line in the heating furnace Exposure time, which is 0.3 s. In the furnace zone, adjust the constant temperature.

The average grain size of the sample 1 to 10 was measured. For samples 1 to 6, the results were in the range of 3 μm to 6 μm, and for samples 7 to 10, the results were in the range of 1.5 μm to 6 μm.

Table 3 below shows the test results obtained with the 8 mm rods of Samples 1 through 6 and the bonded wires.

Table 4 below shows the test results obtained with the 8 mm rod and the bonded wires of samples 7 to 10.

Lines 1-6 and 7-10 produce a program window that is well suited for industrial applications. At least for the nickel content in the range of 0.5 wt.-% to 5 wt.-% or for the silver in the range of 0.1 wt.-% to 0.5 wt.-% and between 0.1 wt.-% and 0.5 wt.- A significant improvement in the corrosion resistance and moisture resistance of the cast rod and the joined ball can be observed in the combination of nickel in the range of %.

Figure 1 is a graph showing an exemplary annealing curve for a nickel alloyed 18 μm copper wire according to Sample 3 (Table 1).

Claims (15)

A core comprising a core comprising or consisting of (a) nickel in an amount ranging from 0.005 wt.-% to 5 wt.-%, (b) optionally, silver, The amount is in the range from 0.005 wt.-% to 1 wt.-%, (c) copper, in an amount ranging from 94 wt.-% to 99.98 wt.-%, and (d) 0 wt.-ppm to 100 wt. The other components of .-ppm, wherein all amounts in wt.-% and wt.-ppm are based on the total weight of the core, wherein the core has an average grain size in the range from 1.5 μm to 30 μm. The average size is determined according to a line intercepting method in which the line has an average diameter in a range from 8 μm to 80 μm. As in the line of claim 1, wherein the average diameter is in the range from 12 μm to 55 μm. A line according to claim 1, wherein the core has a surface as an outer surface, or one of the coating layers is superposed on the surface of the core. The line of claim 3, wherein the mass of the coating is no greater than 2.5 wt.-% relative to the total mass of the core. The line of claim 3, wherein the coating is a single layer of palladium, platinum or silver or a plurality of layers of adjacent layers, each layer being an element selected from the group consisting of palladium, platinum and silver. production. As in the line of claim 3, 4 or 5, another coating is placed over the coating. As in the line of claim 6, wherein the other coating is a gold layer. A line according to claim 1, wherein the core comprises elemental phosphorus as a dopant, and the amount of the elemental phosphorus is in a range from 40 wt.-ppm to 80 wt.-ppm based on the total weight of the core. A line as claimed in claim 1, wherein the ratio between the diameter of the core and the average grain size in the core is in the range from 2 to 14. A line as claimed in claim 1, which is characterized by at least one of the following features: a) corrosion resistance having a value of at most 0% bonded ball peeling; and beta) moisture resistance having a value of at most 0% bonded ball peeling; γ) the hardness of the core is not more than 120HV; δ) If the line has an average diameter of 18μm, the program window area of the stitch bonding has at least 40μm. The value of g; ε) the resistivity of the line is not more than 1.80μΩ. Cm; ζ) if the line has an average diameter of 18 μm, the average bonded ball roundness has a value of at most 0.0025 μm; η) if the line has an average diameter of 18 μm, the average bonded ball concentricity has at most 0.00056 μm value. A method for manufacturing a line as claimed in claim 1, the method comprising at least the following program step (1) providing a precursor item comprising or consisting of: (a) nickel, the amount thereof In the range from 0.005 wt.-% to 5 wt.-%, (b) depending on the case, silver, the amount is in the range from 0.005 wt.-% to 1 wt.-%, (c) copper, the amount is at From 94 wt.-% to 99.98 wt.-%, and (d) 0 wt.-ppm to 100 wt.-ppm of other components, wherein all amounts in wt.-% and wt.-ppm are Based on the total weight of the precursor item, (2) elongating the precursor item to form a line precursor until a desired diameter of the core is obtained; and (3) obtaining the step after completing the program step (2) Annealed by the elongation line precursor. The method of claim 11, wherein the annealing strand is annealed. The method of claim 11, wherein the annealing is performed at a target temperature in the range of 440 ° C to 700 ° C for 0.1 second to 0.4 seconds. The method of claim 11, wherein the annealing is performed at a temperature above a maximum elongation temperature, wherein the line has an elongation value after annealing not greater than 98% of the maximum elongation value. The method of claim 11, wherein the annealing is performed in an inert or reducing atmosphere.