CN111485131A

CN111485131A - Gold bonding wire and preparation method thereof

Info

Publication number: CN111485131A
Application number: CN202010306610.XA
Authority: CN
Inventors: 范红; 李玉芹; 马晓霞; 刘希云; 田晓丹; 李洪磊; 高艳; 姜忠智
Original assignee: Yantai Zhaojin Kanfort Precious Metals Inc Co
Current assignee: Yantai Zhaojin Kanfort Precious Metals Inc Co
Priority date: 2020-04-17
Filing date: 2020-04-17
Publication date: 2020-08-04
Anticipated expiration: 2040-04-17
Also published as: CN111485131B

Abstract

The invention relates to a bonding gold wire and a preparation method thereof, belonging to the technical field of bonding wire processing, wherein the ultra-high strength bonding gold wire comprises the following metal materials, by weight, 10-30ppm of calcium (Ca), 2-20ppm of palladium (Pd), 5-20ppm of lanthanum (L a), 10-30ppm of yttrium (Y), and the balance of gold (Au) with the purity of 99.999 wt%.

Description

Gold bonding wire and preparation method thereof

Technical Field

The invention relates to a gold bonding wire and a preparation method thereof, belonging to the technical field of bonding wire processing.

Background

As the functions of electronic products become more complicated, the electronic products have been unable to satisfy the approach of implementing functions with an increased number of chips. New demands require greater functional integration in smaller volumes. Communication consumer products such as mobile phones are developed in a flat manner, and increased functions mean increased power consumption, and integrated circuits and optoelectronic devices are required to be developed in a thinner and smaller manner in order to reduce power consumption. On the other hand, although the functions of various electronic products are greatly improved, the price is reduced once, and the trend of ultra-thinning and microminiaturization is more obvious under the drive of cost. The main influence of ultra-thinning and microminiaturization of the device on the wire bonding process is the requirement of the wire arc height, and ultra-thinning products require that the bonding wire can adapt to lower arc height conditions without generating neck damage and breakage. The arc height condition that the conventional low-arc bonding gold wire can adapt to is about 2-4 times of the diameter, and the arc height requirement of some ultrathin products can be as low as about 1-2 times of the diameter of the bonding wire. On the other hand, with the development of packaging technology, more and more packaging enterprises have tried to use novel packaging modes such as SIP and the like which save packaging cost, and 2 or more chips with independent functions are packaged into a packaging technology of one chip according to the requirements of terminal clients, so that higher requirements are put forward on wires.

The bonding wire is a micro metal wire inner lead for realizing electrical connection between an input/output bonding point of a circuit in a chip and an inner contact point of a lead frame when a semiconductor device and an integrated circuit are assembled, the main types of the bonding wire comprise gold wire, silver wire, copper wire, palladium-plated copper wire and the like, the share of the gold wire, the silver wire and the copper wire in the market basically forms a three-legged situation, from the aspects of stability and high reliability, the bonding wire is still the main favor of a high-end market, from the development trend of the chip, the chip is developed towards integration and miniaturization, the needed bonding wire is thinner and thinner, the problem of wire punching during packaging is also generated, in order to solve the problems, the mechanical strength of the bonding wire is the most effective means, in addition, L ED manufacturers are used for improving the competitiveness of their products, the standards of internal tests such as cold and heat shock are improved, the thinner bonding wire is used, the standard of cold and heat shock is higher, and the development of the bonding wire is driven to be developed towards the high strength, and the formula of the bonding wire is improved, and the high-strength bonding wire is guaranteed on the basis of high-strength bonding wire (99 wt%).

Disclosure of Invention

The invention aims to solve the defects of the prior art by changing the formula and provide a high-purity bonding gold wire with ultrahigh strength and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a gold bonding wire is characterized by comprising 10-30ppm by weight of calcium (Ca), 2-20ppm by weight of palladium (Pd), 5-20ppm by weight of lanthanum (L a), 10-30ppm by weight of yttrium (Y) and the balance of gold (Au) with a purity of 99.999 wt%.

The gold bonding wire also comprises the following metal materials in percentage by weight: beryllium (Be) 0-10ppm, magnesium (Mg) 0-20ppm, gadolinium (Gd) 0-30 ppm;

a gold bonding wire, which is characterized in that: the metal material comprises the following components in percentage by weight: 10-30ppm of calcium (Ca), 2-20ppm of aluminum (Al), 10-30ppm of cerium (Ce), 10-30ppm of yttrium (Y) and the balance of gold (Au) with the purity of 99.999 wt%.

The gold bonding wire also comprises the following metal materials in percentage by weight: beryllium (Be) 0-10ppm, platinum (Pt) 0-20 ppm;

the preparation method of the gold bonding wire is characterized in that: through the interaction of various trace elements, the mechanical strength of the material is greatly improved on the basis of not influencing the bonding performance, and the method comprises the following steps:

1) preparing materials: weighing various raw materials according to the required weight;

gold nuggets or gold pieces with a purity of 99.999wt%, beryllium pieces with a commercial purity of 99.5wt%, calcium particles with a commercial purity of 99.9wt%, aluminum pieces with a commercial purity of 99.99wt%, magnesium bars with a commercial purity of 99.95wt%, palladium pieces with a commercial purity of 99.95wt%, platinum pieces with a commercial purity of 99.95wt%, cerium nuggets with a commercial purity of 99.5wt%, yttrium pieces with a commercial purity of 99.9wt%, lanthanum pieces with a commercial purity of 99.9wt% and gadolinium pieces with a commercial purity of 99.9 wt%;

2) melting of mother alloy

Determining the melting temperature of each mother alloy according to phase diagrams of Au-Be, Au-Ca, Au-Al, Au-Mg, Au-Pd, Au-Pt, Au-Ce, Au-Y, Au-L a and Au-Gd alloy, melting by a high-frequency furnace, and vacuum protecting (the vacuum degree is 0.1 × 10)^-3Pa), the smelting temperature is 1050-;

melting of Au-X mother alloy

Preparing the master alloy of each added element according to a design scheme.

High-purity gold raw material (with the purity of 99.999 wt%) with the weight proportion of 99.20wt% -99.60wt% and additive elements with the weight proportion of 0.40wt% -0.80wt% are weighed according to the target weight.

a) Feeding: directly putting 90-95% of high-purity gold raw material (99.999 wt%) into a large crucible in a furnace, preparing the rest gold into gold sheets, wrapping the added elements with the gold sheets, and putting the gold sheets into the same crucible;

b) vacuum smelting, namely covering a furnace cover and vacuumizing until the vacuum degree in the furnace reaches 0.1 × 10^-3Heating is started when Pa, the temperature in the furnace is controlled within 1050-1250 ℃ to completely melt the metal, the temperature is maintained for 10-30 minutes, stirring is carried out for 20-30 times, and standing is carried out for 10-40 minutes.

c) And cooling along with the furnace: stopping heating, cooling the molten alloy to room temperature along with the furnace, repeating the step b) for 2-3 times, taking out the master alloy after complete cooling, and tabletting for later use.

3) Drawing and casting gold bar

Adding a trace of alloy element less than 100ppm on the basis of 99.999wt% gold by adopting a vertical continuous casting furnace, and drawing into a 99.99wt% gold rod with the diameter of 5-10 mm.

a) Calculating the weight of the required high-purity gold raw material and various element master alloys according to the design scheme, and respectively weighing gold blocks and master alloy sheets with the purity of 99.999wt% according to the weight percentage so as to ensure that the alloy elements accord with the design scheme and the total amount is less than 100 ppm.

b) Feeding: putting the master alloy into a small suspended crucible in a furnace, and directly putting a high-purity gold raw material into a large crucible in the furnace;

c) vacuum smelting, namely covering a furnace cover and vacuumizing until the vacuum degree in the furnace reaches 0.1 × 10^-3Heating is started when Pa, the temperature in the furnace is controlled within the range of 1050-1250 ℃ to completely melt the gold, and the temperature is maintained for 10-30 minutes. Opening a small suspended crucible in the furnace, adding the master alloy sheet, stirring for 20-30 times, and maintaining the temperature for 10-40 minutes;

d) and drawing and casting the gold bar: stopping vacuumizing, filling argon gas, and adopting a continuous casting method at the speed of 20-60mm/min under the pressure of 0.01-0.05Pa to obtain the gold rod with a smooth surface.

4) And rough drawing: the continuously cast gold rod is drawn into the semi-finished product size required by intermediate annealing through the process. Rough drawing: the elongation of the die is 7-18 percent, and the wire drawing speed is 6-22 m/min.

5) And intermediate annealing: annealing the gold rod obtained by the rough drawing at the temperature of 250-450 ℃ for 2-4h, and cooling along with the furnace.

6) Middle drawing, fine drawing and superfine drawing: and drawing the gold rod subjected to intermediate annealing into the finished product size required by a customer.

a) And middle pulling: the elongation of the die is 9-18%, and the wire drawing speed is 60-180 m/min;

b) fine drawing: the elongation of the die is 4-15%, and the wire drawing speed is 180-;

c) and ultra-fine drawing: the elongation of the die is 4-9%, and the wire drawing speed is 180-.

7) And final annealing:

annealing the gold wire with the finished size at the temperature of 450-.

8) Winding:

winding into the length of the finished product required by the customer, wherein the winding tension is 3-30g, and the winding speed is 500-750 rpm.

9) And packaging:

and (4) placing the wound gold wire into a plastic packaging box, sticking a label, and placing into a paper box for packaging.

The bonding gold wire and the preparation method thereof provided by the invention have the advantages of reasonable and standard process design and simple and convenient operation, and the produced bonding gold wire has high strength and good stability and can completely meet the requirement of high strength of high-purity bonding gold wires.

Drawings

FIG. 1: is a flow chart of the preparation method of the gold bonding wire.

Detailed Description

The following provides a specific embodiment of the present invention for further explaining the constitution of the present invention.

Example 1.

The gold bonding wire of the embodiment is a gold bonding wire with a product model number of K L2C, and is composed of the following metal materials in parts by weight:

10ppm of calcium (Ca), 17ppm of palladium (Pd), 3ppm of magnesium (Mg), 10ppm of lanthanum (L a), 30ppm of yttrium (Y), and the balance of gold (Au) having a purity of 99.999wt%, and its mechanical properties are shown in Table 3.

1) Preparing materials: weighing the following raw materials in parts by weight:

gold lumps or gold sheets with the purity of 99.999wt%, calcium particles with the purity of 99.9wt%, palladium sheets with the purity of 99.95wt%, magnesium strips with the purity of 99.95wt%, lanthanum sheets with the purity of 99.9wt% and yttrium sheets with the purity of 99.9wt% are sold;

2) smelting an Au-X mother alloy:

determining the melting temperature of each mother alloy according to Au-Ca, Au-Pd, Au-Mg, Au-L a and Au-Y alloy phase diagrams, melting with high frequency furnace, and vacuum protecting (vacuum degree of 0.1 × 10)^-3Pa), the smelting temperature is 1050-; preparing a master alloy of each added element according to a design scheme:

b) vacuum smelting, namely covering a furnace cover and vacuumizing until the vacuum degree in the furnace reaches 0.1 × 10^-3Heating at Pa, controlling the temperature in the furnace within 1050-1250 ℃ to completely melt the metal, maintaining the temperature for 10-30 minutes, stirring for 20-30 times, and standing for 10-40 minutes;

c) and cooling along with the furnace: stopping heating, cooling the molten alloy to room temperature along with the furnace, repeating the step b) for 2-3 times, taking out the master alloy after complete cooling, and tabletting for later use;

3) and continuously casting the gold rod:

the equipment used was: vertical continuous casting furnace

The required high purity gold raw material (99.999 wt%) and the weight of each additive element master alloy were calculated and weighed according to the design and target melting weight.

Putting a high-purity gold raw material with the purity of 99.999 percent into a large crucible in a furnace, and putting gold-calcium, gold-palladium, gold-magnesium, gold-lanthanum and gold-yttrium master alloy sheets into a small suspended crucible in the furnace;

covering the furnace cover and vacuumizing until the vacuum degree in the furnace reaches 0.1 × 10^-3Heating is started when Pa, and the temperature is kept for 10-30 minutes when the temperature in the furnace reaches 1050-;

opening a small suspended crucible in the furnace, adding the master alloy sheet, stirring for 20-30 times, maintaining the temperature, and refining for 10-40 minutes;

stopping vacuumizing, filling argon gas, and adopting a continuous casting method at the speed of 20-60mm/min under the pressure of 0.01-0.05Pa to obtain a gold rod with the purity of more than or equal to 99.99%, the diameter of 8 +/-1 mm and a smooth surface;

4) and rough drawing:

a gold rod with the diameter of 8 +/-1 mm is subjected to a rough drawing process to be drawn into a millimeter-grade semi-finished product required by intermediate annealing;

rough drawing: phi 8mm → phi 1.5mm, the die elongation is 7-18%, and the wire drawing speed is 6-22 m/min;

5) and intermediate annealing:

annealing the gold rod obtained by rough drawing at the temperature of 250-450 ℃ for 2-4h, and cooling along with the furnace;

6) middle drawing, fine drawing and superfine drawing:

a) and middle pulling: phi 1.5mm → phi 0.3mm, die elongation of 9-18%, and wire drawing speed of 60-180 m/min;

b) fine drawing: phi 0.3mm → phi 0.08mm, the elongation of the die is 4-15%, and the wire drawing speed is 180-;

c) and ultra-fine drawing: phi 0.08mm → phi 0.015mm, the die elongation is 4-9%, and the wire drawing speed is 180-.

7) And final annealing:

the annealing temperature is 450-;

8) winding:

winding into the length of finished products required by customers, wherein the winding tension is 3-30g, and the winding speed is 500-750 rpm;

9) and packaging:

After a large number of experiments of scientific selection and additive amount adjustment of trace elements, the gold bonding wire of the embodiment achieves a high-strength design target, and also obtains a high neck damage resistance, can adapt to an ultra-low arc application environment on the premise of meeting the conventional lead bonding performance requirements, and has great performance advantages in some ultra-low arc applications and chip-to-chip lead bonding. The method comprises the following specific steps:

1) the height of the wire arc is lower than that of the conventional low wire arc gold bonding wire product (K L1), the wire arc height of the 20 mu m K L1 gold bonding wire is 40-80 mu m, and the wire arc height of K L2C is 20-40 mu m;

2) the neck area is not easy to be damaged;

3) s-shaped bending can be inhibited;

4) the tensile strength of the bonding gold wire is higher than that of the conventional low-wire-arc bonding gold wire, and the tensile strength of the 20 mu m K L1 bonding gold wire is 6.80gf (66.68 mN), and the tensile strength of the K L2C bonding gold wire is 7.76gf (76.10 mN).

Example 2.

The gold bonding wire of this example is different from example 1 in that it is composed of, by weight, 4ppm of beryllium (Be), 15ppm of calcium (Ca), 5ppm of palladium (Pd), 10ppm of magnesium (Mg), 10ppm of lanthanum (L a), 10ppm of yttrium (Y), 30ppm of gadolinium (Gd), and the balance gold (Au) having a purity of 99.999 wt%.

Example 3.

The gold bonding wire of this example was different from example 1 in that it was composed of, by weight, 20ppm of calcium (Ca), 5ppm of palladium (Pd), 20ppm of lanthanum (L a), 30ppm of yttrium (Y), 10ppm of gadolinium (Gd), and the balance of gold (Au) having a purity of 99.999 wt%.

The subsequent process is the same as example 1, and the mechanical properties are shown in Table 3.

Example 4.

The gold bonding wire of the embodiment is a gold bonding wire with a product model number of K L3C, and is composed of the following metal materials in parts by weight:

beryllium (Be) 10ppm calcium (Ca) 20ppm, aluminum (Al) 5ppm, cerium (Ce) 15ppm, yttrium (Y) 20ppm, the balance being gold (Au) with a purity of 99.999 wt%.

The subsequent process is the same as example 1, and the mechanical properties are shown in Table 4.

After a large number of experiments of scientific selection of trace elements and adjustment of addition amount, the mechanical strength of the gold bonding wire of the embodiment reaches and exceeds that of a gold wire type with 99% gold content on the premise of maintaining 99.99% gold content of the product. The product has the advantage of high tensile force when used on common integrated circuit products and photoelectric device products. The method has performance advantages on some BGA products with super-large size and high pin count and some SIP products with large size. The method comprises the following specific steps:

compared with K L2C, the tensile strength of the 20 mu m common bonding alloy wire is 6.80gf (66.68 mN), the tensile strength of the K L3C common bonding alloy wire is 8.51gf (83.45 mN), and the method is more suitable for packaging high-density micro chips.

Example 5.

The gold bonding wire of the present embodiment is different from that of embodiment 4 in that: the alloy consists of the following metal materials in percentage by weight: 30ppm of calcium (Ca), 8ppm of aluminum (Al), 12ppm of platinum (Pt), 20ppm of cerium (Ce), 10ppm of yttrium (Y), and the balance of gold (Au) with the purity of 99.999 wt%.

The subsequent process is the same as that of example 1, and the mechanical properties are shown in Table 4.

Example 6.

The gold bonding wire of the present embodiment is different from that of embodiment 4 in that: the alloy consists of the following metal materials in percentage by weight: beryllium (Be) 4ppm, calcium (Ca) 24ppm, aluminum (Al) 2ppm, cerium (Ce) 30ppm, yttrium (Y) 10ppm, and the balance of gold (Au) with a purity of 99.999 wt%.

According to the bonding gold wire produced according to the formula and the process steps, the existence of the alloy elements can improve the strength and the rigidity of the gold wire, the ultrahigh-strength bonding gold wire can be prepared, the wire impact resistance after wire bonding and packaging can be improved, and the yield and the reliability of a device can be improved.

The physical properties of the ultra-high strength and high purity gold bonding wire product prepared according to the formula and the process steps are shown in the table 1, and the established mechanical property standard is shown in the table 2:

TABLE 1 physical Properties of ultra-high strength gold bonding wire

TABLE 2 mechanical property standard of ultra-high strength gold bonding wire

Compared with the prior art, the ultra-high strength and high purity bonding gold wire produced by the invention has the following technical comparisons:

the gold bonding wire with the diameter of 20 μm was selected for mechanical property parameter comparison, as shown in tables 3 and 4. As can be seen from the data in the table, the strength of the ultra-high strength and high purity gold bonding wire (99.99 wt%) produced by the company is improved by 8-20% compared with the conventional model.

Comparison of mechanical properties of gold bonding wires of 320 mu m in table

TABLE 420 μm comparison of mechanical properties of gold bonding wires

The invention aims to determine the influence of different types and different contents on the bonding performance of the bonding gold wire by adding different elements, develop an ultrahigh-strength high-purity bonding gold wire product with the strength exceeding the level of the existing like product, and determine a production process and key parameters so as to meet the thinning requirement brought by the integration and miniaturization trend of a semiconductor device.

1) Selecting proper alloy elements, determining the content of the alloy elements, and obtaining a gold rod by adopting a continuous casting method;

2) determining an ideal die machining rate and a wire drawing rate in a wire drawing process;

3) determining an ideal intermediate annealing wire diameter and annealing temperature in the wire drawing process;

4) and determining the ideal final annealing temperature, winding tension and winding speed.

The gold bonding wires of the embodiments can be widely applied to the requirements of high-density space, stacked package and ultra-thin package in large-scale and ultra-large-scale integrated circuits such as DIP, SIP, QFP, BGA, CSP and the like.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention, such as the content of raw materials, should be included in the protection scope of the present invention.

Claims

1. A gold bonding wire is characterized by comprising 10-30ppm by weight of calcium (Ca), 2-20ppm by weight of palladium (Pd), 5-20ppm by weight of lanthanum (L a), 10-30ppm by weight of yttrium (Y) and the balance of gold (Au) with a purity of 99.999 wt%.

2. The gold bonding wire of claim 1, wherein: the metal material also comprises the following metal materials in percentage by weight: beryllium (Be) 0-10ppm, magnesium (Mg) 0-20ppm, gadolinium (Gd) 0-30 ppm.

3. A gold bonding wire, comprising: the metal material comprises the following components in percentage by weight: 10-30ppm of calcium (Ca), 2-20ppm of aluminum (Al), 10-30ppm of cerium (Ce), 10-30ppm of yttrium (Y) and the balance of gold (Au) with the purity of 99.999 wt%.

4. A gold bonding wire as defined in claim 3, wherein: the metal material also comprises the following metal materials in percentage by weight: beryllium (Be) 0-10ppm, platinum (Pt) 0-20 ppm.

5. The method for preparing gold bonding wire as claimed in any one of claims 1 to 4, wherein: the method comprises the following steps:

2) and smelting the Au-X mother alloy:

determining the melting temperature of each mother alloy according to Au-X alloy phase diagram, melting by high frequency furnace under vacuum protection with vacuum degree of 0.1 × 10^-3PaThe smelting temperature is 1050-;

3) and drawing and casting the gold bar:

adding trace less than 100ppm of alloy elements on the basis of 99.999wt% of gold by adopting a vertical continuous casting furnace, and drawing into a 99.99wt% gold rod with the diameter of 5-10 mm;

4) and rough drawing: drawing the continuously cast gold rod into a semi-finished product size required by intermediate annealing through the process;

5) and intermediate annealing: annealing the gold rod obtained by rough drawing at the temperature of 250-450 ℃ for 2-4h, and cooling along with the furnace;

6) middle drawing, fine drawing and superfine drawing: drawing the gold bar subjected to intermediate annealing into a finished product size required by a customer;

7) and final annealing:

annealing the gold wire with the finished size at the temperature of 450-.

6. The method for preparing gold bonding wire according to claim 5, wherein: further comprising the steps of:

8) winding:

9) and packaging:

7. The method for preparing gold bonding wire according to claim 5, wherein: the step 2) of smelting the Au-X mother alloy comprises the following steps:

weighing 99.20-99.60 wt% of high-purity gold raw material, 99.999wt% of purity and 0.40-0.80 wt% of additive element according to the target weight;

a) feeding: directly putting 90-95% of high-purity gold raw material into a large crucible in a furnace, preparing the rest gold into gold sheets, wrapping the added elements with the gold sheets, and putting the wrapped elements into the same crucible;

8. The method for preparing gold bonding wire according to claim 5, wherein: the step 3) of drawing and casting the gold rod comprises the following steps:

a) calculating the required high-purity gold raw material and the weight of various element master alloys according to the design scheme, and respectively weighing gold blocks and master alloy sheets with the purity of 99.999wt% according to the weight percentage so as to ensure that the alloy elements conform to the design scheme and the total amount ratio is less than 100 ppm;

c) vacuum smelting, namely covering a furnace cover and vacuumizing until the vacuum degree in the furnace reaches 0.1 × 10^-3Heating at Pa, controlling the temperature in the furnace to be within 1050-1250 ℃ to completely melt the gold, and maintaining the temperature for 10-30 minutes; opening a small suspended crucible in the furnace, adding the master alloy sheet, stirring for 20-30 times, and maintaining the temperature for 10-40 minutes;

9. The method for preparing gold bonding wire according to claim 5, wherein: the process parameters of the step 4) and the rough drawing are as follows: the elongation of the die is 7-18 percent, and the wire drawing speed is 6-22 m/min.

10. The method for preparing gold bonding wire according to claim 5, wherein: the process parameters of the step 6), the intermediate drawing, the fine drawing and the ultra-fine drawing are as follows: