TWI796739B - Alloy bonding wire - Google Patents

Abstract

An alloy bonding wire is provided. The alloy bonding wires contain a base material of Ag, Cu, or Al added with 0.001~2wt% of Ge. When the base material is Cu or Al, the alloy bonding wire may further contain 0.001~10wt% of at least one of Pt, Pd, Cu, Au, Ni, Si, and Sc elements. When the base material is Ag, the alloy bonding wire may further contain 0.001~10wt% of at least one of Pd, Cu, Au, Ni, Si, and Sc elements.

Description

Alloy wire

The present invention relates to an alloy welding wire, and in particular to an alloy welding wire used for electronic package wire bonding.

Wire bonding is the main interconnection method in the packaging process of integrated circuits (IC) and light emitting diodes (LED). In addition to providing signal and power transmission between the chip and the substrate, the wire bonding wire can also have the function of heat dissipation. Therefore, the wire bonding wire must have high electrical conductivity, high thermal conductivity, sufficient strength and ductility. However, in order to avoid the cracking of the chip caused by the hot-pressing process of wire bonding, and to ensure good contact between the wire and the pad to ensure good bonding, the hardness of the wire should not be too high. Since the polymer sealant for packaging often contains corrosive chloride ions, and the polymer sealant itself has environmental hygroscopicity, the wire must have good oxidation resistance and corrosion resistance.

In the wire bonding process, the end of the wire must first be fused by high-voltage discharge (Electric Flame Off, EFO), and the surface tension is used to form a ball (Free Air Ball, FAB). The welding pads are bonded to form a first welding point, and the other end of the wire is pulled to another conductive welding pad and joined with another conductive welding pad to form a second welding point, thereby forming a circuit conduction. The shape of the ball determines the quality of the subsequent first ball bond. In addition, intermetallic compounds are formed at the bonding interface between the first ball pad and the pad of the semiconductor chip. These intermetallic compounds can ensure interfacial bonding, but excessive intermetallic compounds can cause interface brittle cracks and Kirkendall voids. In addition, the anti-oxidation and corrosion resistance of the wire itself are the elements that determine the reliability of electronic products.

When the packaging of the semiconductor or light-emitting diode is completed, the high current density passing through the wire may also drive the internal atoms to generate electromigration (Electron Migration) during the use of the product, causing holes to form at one end of the wire, thereby reducing electrical conductivity and thermal conductivity, and even Cause disconnection and product failure; the current may also cause partial melting of the packaging wire, causing the voltage to rise rapidly, and finally lead to disconnection and product failure. This problem is especially serious for the packaging of high-voltage and high-current electronic products. The main factor of product reliability.

Currently common packaging wires, for example, include the following options:

(1) Gold wire: Gold wire can have low resistivity, but a large number of brittle intermetallic compounds (including Au ₂ Al, AuAl ₄ , Au ₅ Al _{2 ,} etc.) will be formed at the bonding interface between gold wire and aluminum pad, making the conductivity reduce. In addition, the intermetallic reaction at the gold/aluminum interface will produce many Kirkendall voids, which will further increase the resistivity of the joint interface, resulting in a decrease in the reliability of the joint.

(2) Copper wire: In recent years, the packaging industry has begun to use copper wire as the wire bonding wire for semiconductors and light-emitting diodes. Although copper wire has good electrical conductivity, it is easy to oxidize. Therefore, the storage and transportation of wire rods need to be sealed and protected. The wire bonding process requires expensive nitrogen and hydrogen assistance. Will encounter oxidation and corrosion problems. In addition, the material of the copper wire is too hard, and the wire bonding is likely to cause problems such as cracking of the chip. Although it has been proposed in some studies to plate other metal coatings on the surface of copper wires to improve the oxidation and corrosion problems (for example, refer to US Patent No. It is easy to fail, so it still cannot achieve the reliability required for packaging high-voltage and high-current electronic products.

(3) Silver wire: Silver is the element with the lowest resistivity among all materials, but pure silver will have the problem of sulfide corrosion in a sulfur-containing environment, and at the same time, pure silver wire will also generate brittle intermetallic compounds when bonding on aluminum pads ( Ag ₂ Al or Ag ₄ Al). In addition, pure silver wires are prone to electrolytic ion migration (Ion Migration) inside the packaging material containing moisture. That is to say, pure silver will hydrolyze and dissolve silver ions through the action of electric current in the environment containing water and gas, and then react with oxygen to become unstable silver oxide (AgO). Silver whiskers grow out of leaf veins, and finally cause a short circuit between the positive and negative electrodes (please refer to: H. Tsutomu, Metal Migration on Electric Circuit Boards, Three Bond Technical News, Dec. 1, 1986.). In addition, in some studies, it is proposed to plate other metal coatings on the surface of silver wires to improve the problems of sulfide corrosion and silver ion migration (for example, refer to US Patent No. 6,696,756), but the formed wires still cannot achieve ideal reliability and resistance. Rate.

(4) Alloy wire: The alloy wire includes, for example, gold-based alloys and silver-based alloys. These alloys include, for example, elements such as copper, platinum, manganese, chromium, calcium, indium, etc. However, these alloy wires still cannot have properties of low impedance and high reliability at the same time.

To sum up, the existing pure metal wires, metal-coated composite wires, and alloy wires with added elements cannot meet all the packaging requirements. Therefore, there is still a need for a wire with high reliability.

Some embodiments of the present disclosure provide an alloy bonding wire, the base material of which is any one of silver, copper or aluminum, including 0.001 to 2 wt.% of Ge, and the rest of the base material.

In some embodiments, the alloy wire is a binary alloy wire.

In some embodiments, the base material of the alloy welding wire is copper or aluminum, and further includes an additional element obtained from at least one of Pt, Pd, Cu, Au, Ni, Si or Sc, and the total amount of the added element is 0.001 to 10 wt.%.

In some embodiments, the base material of the alloy wire is silver, and further includes an additional element obtained from at least one of Pd, Cu, Au, Ni, Si or Sc, and the total amount of the added element is 0.001 to 10wt. %.

In some embodiments, the alloy wire is a round wire.

In some embodiments, the alloy wire has a diameter of 10 μm to 300 μm.

In some embodiments, the alloy wire is a flat ribbon wire.

In some embodiments, the alloy wire has a thickness of 20 μm to 300 μm.

In some embodiments, the alloy wire has a width of 100 μm to 2000 μm.

In some embodiments, the alloy bonding wire further includes a surface coating, the surface coating includes Au, Pd, Pt, alloys thereof or a combination thereof, and the thickness of the surface coating is 0.01 to 10 μm.

The following disclosure provides a number of embodiments, or examples, for implementing different elements of the provided subject matter. Specific examples of each component and its configuration are described below to simplify the description of the embodiments of the present invention. Of course, these are just examples, not intended to limit the embodiments of the present invention. For example, if a description mentions that a first element is formed on a second element, it may include an embodiment in which the first and second elements are in direct contact, or may include an additional element formed between the first and second elements , so that they are not in direct contact with the example. In addition, the embodiments of the present invention may repeat reference numerals or letters in various examples. This repetition is for the purpose of brevity and clarity and not to show the relationship between the different embodiments or configurations discussed.

Furthermore, terms relative to space may be used, such as "below", "below", "lower", "above", "higher", etc., for the convenience of description The relationship between one component or feature(s) and another component(s) or feature(s) in a drawing. Spatially relative terms are intended to encompass different orientations of the device in use or operation, as well as orientations depicted in the drawings. When the device is turned to a different orientation (rotated 90 degrees or otherwise), the spatially relative adjectives used therein shall also be interpreted in accordance with the turned orientation.

When the terms "about", "approximately" and similar terms are used herein to describe numbers or numerical ranges, the terms are intended to cover values that include the stated number within a reasonable range, such as +/- 10% of the stated number. %, or other values understood by those skilled in the art to which the present invention pertains. For example, the phrase "about 5 nm" encompasses a size range from 4.5 nm to 5.5 nm.

The terms used herein are used to illustrate specific embodiments only, and are not intended to limit the inventive concepts. The expressions used in the singular also encompass the expressions in the plural unless the expressions have clearly different meanings in the context. In this specification, it should be understood that terms such as "comprising", "having", and "including" are intended to indicate the existence of the features, numbers, steps, actions, components, components or combinations thereof disclosed in this specification, and It is not intended to exclude the possibility that one or more other features, numbers, steps, actions, components, parts or combinations thereof may be present or may be added.

The present disclosure provides an alloy welding wire, which is composed of adding 0.001 to 2wt.% of Ge to a silver, copper or aluminum substrate, and adding 0.001 to 10wt.% selected from Pt, Pd, Cu, Au, Ni, Si, Or at least one additional element in Sc, this alloy composition can improve the high temperature creep resistance, sulfidation resistance, oxidation resistance and gloss of the welding wire, so it has excellent reliability.

The US8101123B2 patent discloses a silver alloy wire composed of Ag-Au-Pd. Although the addition of Au and Pd to the Ag alloy composition can improve the mechanical properties and oxidation resistance of pure silver wire, and the addition of Pd can slow down the silver ion migration problem, however The alloy wire rod of this composition has poor creep resistance at high temperature, and its sulfidation resistance, oxidation resistance and luster are also poor. The US20130171470 patent discloses a silver alloy wire composed of Ag-Au-Pd and whose grain structure exhibits a large number of annealing twins. Oxidability and luster were also insufficient. Patents such as JP1997275120, US20080240975A1, CN10215454A, US20130126934, TWI408787, and US10840208B2 add Pt and other trace elements to the Ag alloy. However, the silver alloy wire rods of these known technologies also have insufficient high-temperature creep resistance, and their gloss and sulfidation resistance are also insufficient. Both are poor.

In this case, by adding 0.001 to 2wt.% Ge to the silver, copper or aluminum substrate, the high temperature creep resistance can be significantly improved, and its sulfidation resistance, oxidation resistance and gloss are also improved. In some embodiments, if the content of germanium is too high, the ductility of the bonding wire may be reduced. In addition to Ge, the bonding wire in this case can add 0.001 to 10wt.% of at least one additional element selected from Pt, Pd, Cu, Au, Ni, Si, or Sc, which can increase the strength of the bonding wire and further improve The anti-oxidation and chloride ion corrosion resistance of the welding wire also reduces the formation of intermetallic compounds between the silver alloy wire and the aluminum pad. In some embodiments, if the content of these third elements is too high, the resistivity of the bonding wire may be significantly increased.

According to some embodiments, FIG. 1 is a round alloy welding wire 10 in a first form of the present disclosure. Fig. 1 is a part of the line segment of the round alloy welding wire 10, the base material of the round alloy welding wire 10 is silver, copper or aluminum, which includes 0.001 to 2wt.% Ge and the base material of the balance, such as about 0.01 to About 1 wt % or about 0.05 to about 2.0 wt % Ge. According to some embodiments, alloy wire 10 is a binary alloy wire, ie, contains only Ge in addition to the base material. According to some embodiments, the base material of the alloy welding wire 10 is copper or aluminum, and the alloy welding wire 10 further includes an additional element selected from at least one of Pt, Pd, Cu, Au, Ni, Si, or Sc, and the above-mentioned The total amount of added elements is 0.001 to 10 wt.%, for example about 0.01 to about 1 wt.% or about 0.05 to about 5 wt.%. According to some embodiments, the base material of the alloy welding wire 10 is silver, and the alloy welding wire 10 further includes an additive element selected from at least one of Pd, Cu, Au, Ni, Si, or Sc, and the total of the above additive elements The added amount is 0.001 to 10 wt.%, such as about 0.01 to about 1 wt.% or about 0.05 to about 5 wt.%. It should be noted that when the base material of the alloy bonding wire 10 is silver, Pt is not included in the above-mentioned additive elements. Wherein the silver, copper or aluminum substrate is substantially pure silver, pure copper or pure aluminum. The round alloy wire 10 has a diameter of about 10 μm to about 300 μm, such as about 100 μm to 200 μm or about 50 μm to 250 μm.

In some embodiments, the above-mentioned round alloy wire can also be uniformly coated with a surface coating on the outer layer, as shown in FIG. 2A to FIG. 2B , and FIG. 2B is a longitudinal section view along the longitudinal direction of FIG. 2A . The surface coating 22 may include substantially pure gold, substantially pure palladium, substantially pure platinum, alloys thereof, or combinations thereof. The surface coating 22 can be formed by an appropriate coating method (for example: electroplating, sputtering and vacuum evaporation). Due to the chemical inertness of the material of the surface coating 22, the circular alloy welding wire 20 inside can be protected from corrosion, and at the same time, it has a lubricating effect when the wire is drawn, and the thickness of the surface coating 22 is about 0.01 to about 10 μm. For example about 0.1 μm to about 5 μm or about 1 μm to about 8 μm.

According to some embodiments, FIG. 3 is a flat strip-shaped alloy welding wire 30 in the second form of the present disclosure. Fig. 3 is a part of the flat strip-shaped alloy welding wire 30. The material and additive elements of the flat strip-shaped alloy welding wire 30 can refer to the round alloy welding wire 10 shown in Fig. 1, and will not be repeated here. According to some embodiments, the thickness of the flat alloy wire 30 is from about 20 μm to about 300 μm, such as from about 50 μm to about 125 μm or from about 100 μm to about 250 μm. According to some embodiments, the flat strip-shaped alloy wire 30 has a width of about 100 μm to about 2000 μm, such as about 500 μm to about 1400 μm or about 1000 μm to about 1800 μm. It is worth noting that, in some embodiments, the above-mentioned flat strip-shaped alloy welding wire can also be uniformly coated with a surface coating on the outer layer, as shown in Figures 4A to 4B, where Figure 4B is the longitudinal direction of Figure 4A longitudinal section view. As mentioned above, the surface coating 42 can protect the alloy welding wire 30 therein from corrosion, and at the same time play a lubricating effect when the wire is drawn and formed. Surface plating 42 may include substantially pure gold, substantially pure palladium, substantially pure platinum, alloys thereof, or combinations thereof. The surface coating 42 can be formed by an appropriate coating method (for example: electroplating, sputtering and vacuum evaporation), and the thickness of the surface coating 42 is about 0.01 to about 10 μm, such as about 0.1 μm to about 5 μm or about 1 μm to about 8.5 μm.

Regarding the substantially pure metal mentioned in the specification, taking pure silver as an example, it refers to pure silver that is expected to be completely free of impurities such as other elements and compounds in design, but it is difficult to completely remove it during the actual smelting, refining, coating, etc. Removing the above-mentioned impurities and achieving mathematically or theoretically 100% pure silver is regarded as "substantially pure silver". Therefore, in other embodiments, the alloy welding wire and/or its plating layer may further include other metals, non-metals Elements, or other impurity components, and when the range of the above-mentioned impurity content falls within the acceptable range stipulated in the corresponding standards or specifications. Those with ordinary knowledge in the technical field of the present invention should understand that the above-mentioned corresponding standards or specifications will be different according to different properties, conditions, requirements, etc., so no specific standards or specifications are listed in this document.

In some embodiments, the forming method of the above-mentioned alloy welding wire may be to form a thick wire first, and then alternately perform a plurality of cold forming steps and a plurality of annealing steps, so as to successively reduce the diameter of the thick wire. The thick wire rod can be formed by heating and melting the alloy, and then casting it to form an ingot. The ingot is then cold worked to form thick wire. In some embodiments, the above-mentioned cold forming step includes wire drawing, extrusion or a combination thereof. Alternatively, the above-mentioned cold forming step and annealing step can be any known or future developed cold working/annealing methods.

10: Round alloy welding wire 20: round alloy welding wire 22: Surface coating 30: flat strip alloy welding wire 40: flat strip alloy welding wire 42: Surface coating

Various aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that, in accordance with the standard practice in the industry, the various features are not drawn to scale and are used for illustrative purposes only. In fact, the dimensions of the elements may be arbitrarily expanded or reduced to clearly illustrate the features of the present disclosure. Figure 1 illustrates a portion of a circular alloy wire, according to some embodiments. FIG. 2A depicts a portion of a circular alloy bonding wire with a surface plating, according to some embodiments. FIG. 2B shows a longitudinal section along the length of a round alloy wire with a surface plating as shown in FIG. 2A , according to some embodiments. Figure 3 depicts a portion of a flat ribbon-shaped alloy wire, according to some embodiments. FIG. 4A depicts a portion of a flat ribbon-shaped alloy bonding wire with a surface plating, according to some embodiments. Figure 4B shows a longitudinal section along the length of the flat ribbon-shaped alloy wire with the surface plating shown in Figure 4A, according to some embodiments.

20: round alloy welding wire 22: Surface coating

Claims (7)

A kind of alloy welding wire, its base material is any one in silver, copper or aluminum, and it comprises the Ge of 0.001 to 2wt.%, and the balance base material, wherein when the base material is copper, it further includes Pt, Ni, Addition of at least one of Si or Sc, the total addition of the addition is 0.001 to 0.01wt.%; when the base material is aluminum, it also includes the addition of at least one of Pt, Pd, Au, Ni or Sc element, the total amount of the added element is 0.001 to 0.01wt.%; when the base material is silver, it further includes an added element from at least one of Pd, Au or Sc, and the total added amount of the added element is 0.001 to 0.01 wt.%. The alloy welding wire according to claim 1, wherein the alloy welding wire is a round welding wire. The alloy welding wire according to claim 2, wherein the alloy welding wire has a diameter of 10 μm to 300 μm. The alloy welding wire according to claim 1, wherein the alloy welding wire is a flat strip-shaped welding wire. The alloy welding wire according to claim 4, wherein the thickness of the alloy welding wire is 20 μm to 300 μm. The alloy welding wire according to claim 4, wherein the alloy welding wire has a width of 100 μm to 2000 μm. The alloy bonding wire according to any one of claims 1 to 6, further comprising a surface coating, the surface coating contains Au, Pd, Pt, alloys thereof or a combination thereof, and the thickness of the surface coating is 0.01 to 10 μm.

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