TWI471899B - Silver-based biphasic electrothermal resistance wire and manufacturing method thereof - Google Patents

Description

Electric heating silver-based two-phase line and manufacturing method thereof

The present invention relates to an electric heating-resistant silver-based two-phase wire and a manufacturing method thereof, and particularly to an electrothermal-resistant silver-based two-phase wire suitable for a semiconductor package, an IC package or a light-emitting diode package, and a manufacturing method thereof. The doped nano-aluminum particles enter the silver wire, and the chrome-plated layer on the surface of the silver is further heat-treated to form a silver-based two-phase line with Ag ₂ Cr and AgAl ₇ Cr phases, thereby increasing the resistance of the silver-based two-phase line. Oxidation and thermal stability and the ability to maintain excellent resistance to fusing current, while controlling the residual chrome plating layer under appropriate heat treatment conditions, making it a non-plated thermal diffusion wire, which can effectively suppress the thickness of intermetallic compound formation at the wire bonding interface (such as Ag). ₂ Al or Ag ₄ Al), and maintain the low resistance characteristics of the silver-based two-phase line circuit.

According to the low electrical resistivity, it is a basic requirement for general electronic product packaging wires, and for high-speed operation and high-frequency integrated circuit components (such as high-speed amplifiers, oscillators, power management integrated circuits, and high-speed communication components, etc.) In order to avoid signal delaying and cross talk interference, the resistivity of the wire is more stringent; in addition, to ensure that the product can maintain normal life and function under long-term and severe conditions (weathering Sexuality, reliability considerations are also extremely important; therefore, the packaging industry needs to be able to combine low-impedance and high-reliability wire bonding wires.

At present, common package wires include gold wire, copper wire, silver wire, alloy wire, etc. Taking silver wire as an example, silver is the lowest resistivity element among all materials, and the pure silver wire is also generated when wire bonding is performed on the aluminum pad. Brittle boundary metal compounds (Ag ₂ A l or Ag ₄ Al); in addition, pure silver wires are prone to ion migration within the aqueous gas encapsulating material, that is, pure silver passes current in an aqueous gas environment. The action dissolves and dissolves the silver ions, and then reacts with oxygen to become unstable silver oxide (AgO), which deoxidizes to form silver atoms, and grows silver of leaf veins toward the positive electrode. It must cause a short circuit between the positive and negative electrodes; therefore, the current pure silver wire does not provide the spheroidality and stability required by the industry; therefore, there are silver-based alloy wires (including copper, platinum, manganese, chromium, gold, etc.). As an encapsulating wire, the formed wire still cannot have the properties of low impedance and high reliability, that is, it cannot pass the high temperature oxidation test, and there is no increase in the fusing current density; for example, please refer to The "silver-based alloy wire and its manufacturing method" disclosed in the Chinese Patent Publication No. I394849 discloses a silver-based alloy wire which is an alloy wire formed of at least silver, palladium, rhodium and platinum. The amount of palladium (Pd) is effective to improve the oxidation resistance and sulfur corrosion resistance of silver wire. At the same time, due to its extremely low diffusion rate and barrier properties of surface products, the ion migration of silver can be avoided, and for silver and aluminum pads. The interfacial metal reaction also has an inhibitory effect; and an appropriate amount of germanium (Ge) can effectively improve the oxidation resistance and vulcanization of the wire, and at the same time improve the joint strength of the solder joint; in addition, an appropriate amount of platinum (Pt) can enhance the oxidation resistance of the wire. Sulphide and chloride ion corrosive, and also have a significant inhibitory effect on the ion transport phenomenon of silver, and also reduce the formation of metal compounds between the silver alloy wire and the aluminum pad; however, the above-mentioned silver-based alloy wire needs to be accurately produced ( Ppm grade) is formulated with the composition ratio of palladium, rhodium and platinum. If the content of palladium is too high, the electrical resistance of the alloy wire will increase. If the content of plutonium is too high, it will cause The ductility of the material is lowered, and when the content of platinum is too high, the electrical resistivity of the wire is remarkably improved, so that it is not easy to maintain the consistency of reliability during manufacture; in addition, the wire cannot pass the high temperature oxidation test without improvement The effect of fusing current density.

In addition, in order to solve the problem of easy oxidation of pure silver bonding wire, some companies have proposed to apply other metal plating on the surface to improve the oxidation and corrosion. Please refer to Nippon Steel High-tech Materials Co., Ltd. and Nippon Steel Micro Metals Co., Ltd. limited The company has applied for a series of inventions relating to the wiring of semiconductor devices, the invention patent of the Republic of China, the "connection wire for semiconductor devices" disclosed in the announcement No. I342809, the "connection wire for semiconductor devices" disclosed in the announcement No. I364806, and the disclosure of the publication No. I364806. "Semiconductor bonding wire", "Calcium bonding wire for semiconductors" of the publication No. 201107499, "Current bonding wire for semiconductors and bonding structure thereof" of the publication No. 201140718, and "Joining structure of a plurality of layers of copper bonding wires" The bonding wire structure of the above-mentioned previous case is generally attached to a core material (which may be composed of a metal such as copper, gold or silver) provided with a skin layer (which may be composed of palladium, rhodium, iridium, platinum, and silver). Therefore, the above-mentioned bonding wire often causes the following defects when it is actually used: (a) the metal-plated wire has a skin layer on its surface, so that the hardness is high, and the process current control is not easy, often resulting in uneven thickness of the plating layer, resulting in uneven thickness of the plating layer. The overall yield of the packaging process is poor, and the yield is low; (b) the palladium layer is plated with silver or silver alloy in the case of electric frame off (EFO), due to the surface palladium The core of the free air ball (FAB) is too hard, resulting in insufficient strength of the neck above the solder ball. After wire bonding (WB), the neck fracture problem often occurs, which leads to the problem of joint interface peeling. Occurs; and the palladium element also has a segregation problem in the solder ball, and the difference in the structure of the ball portion greatly affects the wire bonding condition; further, the wire cannot maintain the surface oxidation resistance in a high temperature environment, and the atmosphere protection strip is required when the ball is formed. Next, otherwise you can't make a ball.

In addition, the general bonding wire must be protected by a thermosetting plastic (for example, epoxy resin (EPOXY) after the wire is wired; however, the epoxy material may be lit at a high temperature or for a long time. Problems such as light degradation or yellowing cannot meet the quality requirements of the process reliability of the LED packaging industry, and the wire cannot effectively suppress the stability of the negative ion etching surface and the long-time high humidity and high heat environment.

Nowadays, the inventor is that in view of the above-mentioned existing silver-based alloy wire or bonding wire for packaging, there are still many defects in the actual implementation, so that it is not a The spirit of tiredness, and with the help of its rich professional knowledge and years of practical experience, has been improved and the invention has been developed accordingly.

The main object of the present invention is to provide an electrothermal-resistant silver-based two-phase line and a manufacturing method thereof, in particular to a process for entering a silver wire by doping nano-pure aluminum particles and chrome plating on a silver base surface. Ag ₂ Cr and AgAl ₇ Cr phases are formed on the surface of the silver base to improve the oxidation resistance and thermal stability of the silver-based biphasic line. At the same time, the residual chromium plating layer is controlled by appropriate heat treatment conditions, and the intermetallic compound formation is effectively suppressed. The thickness, in turn, maintains the low resistance characteristics of the silver-based two-phase line loop.

In order to achieve the above-mentioned object, the present inventors propose an electrothermal-resistant silver-based two-phase line and a method for producing the same, which are firstly formed in a silver wire with not more than 8 wt.% of nano-aluminum particles, preferably 3 wt. .%~8wt.% of nano-aluminum particles, and the aluminum particles are evenly distributed in the silver base, so that the silver wire is formed into a silver baseline; wherein the aluminum particles have a particle size of between 10 and 20 nm; a chromium layer having a thickness of not less than 32 nm is preferably plated on the surface of the silver base, preferably between 32 nm and 106 nm. Finally, the silver base plated with the chromium layer is heat-treated to cause the chromium ions of the chromium layer to enter the silver. a base base, and an anti-oxidation layer formed on the surface of the silver base, wherein the oxidation resistant layer comprises one or a combination of an Ag ₂ Cr phase or an AgAl ₇ Cr phase to form a silver-based two-phase line; The Ag ₂ Cr and AgAl ₇ Cr phases formed by heat treatment can improve the oxidation resistance of the electrothermal silver-based double-phase wire of the present invention, especially the high-temperature oxidation resistance property, and avoid the ring for sealing the bonding wire. Oxygen resin material due to photothermal degradation or yellowing, and due to silver base No abnormal internal phase of coarse grains, and has a high temperature strength of the wire strength of bonding interface does not weaken the effect, but also enhance its mechanical properties and thermal stability.

In an embodiment of the invention, the method of forming nano-aluminum grains in a silver wire is to add aluminum particles to the silver melt soup, stir and uniformly mix, preferably by vacuum electromagnetic stirring.

In an embodiment of the invention, the heat treatment is heated to 400~ a temperature of 700 ° C, and the temperature is continued for less than 1 hour, so that the chromium ions of the chromium layer completely or partially enter the silver baseline base, that is, the thickness of the residual chromium plating layer is between 0 and 71 nm; thereby, with appropriate The heat treatment condition controls the residual chrome plating layer, so that the thickness of the interface intermetallic compound is effectively suppressed after the wire is formed into a ball, thereby maintaining the low resistance characteristic of the silver-based two-phase line circuit.

In addition, the electrothermal silver-based biphasic line of the present invention has two structural aspects due to different heat treatment conditions; the system includes a silver base line and an anti-oxidation layer surrounding the silver baseline surface, and the silver baseline has no more than 8 wt.%. Nano-aluminum particles, and the oxidation resistant layer comprises one or a combination of Ag ₂ Cr phase or AgAl ₇ Cr phase; another thermoelectric resistant silver-based biphasic line includes a silver baseline and a silver-containing baseline surface The anti-oxidation layer and a chromium layer surrounding the surface of the oxidation resistant layer.

(S1)‧‧‧Step one

(S2)‧‧‧Step 2

(S3) ‧ ‧ Step 3

The first figure is a flow chart of the manufacturing method of the preferred embodiment of the present invention. The second figure: the silver base line of the embodiment of the present invention has a microscope structure with only an anti-oxidation layer after the heat treatment. The silver base of the second embodiment of the present invention has a microstructure of the anti-oxidation layer and the chromium layer on the surface of the silver after heat treatment. [Embodiment] The object of the present invention and its structural and functional advantages will be based on the following drawings. The structure of the present invention will be described in conjunction with specific embodiments, so that the reviewing committee can have a deeper and more specific understanding of the present invention.

First, the electrothermal silver-based dual-phase line system of the present invention is suitable for packaged wires of electronic industrial parts such as semiconductor packages, IC packages, LED packages, etc. The manufacturing method of the specific embodiment includes the following steps, please refer to the first figure. Show: Step 1 (S1): Forming no more than 8 wt.% of nano-aluminum particles in a silver wire, and uniformly distributing the aluminum particles in a silver base, doping or adding by aluminum metal particles Increasing the strength of the silver base line and retaining its ductility without reducing the fusing current density; wherein, in step one (S1), for example, no more than 8 wt.% of the nano-aluminum particles are added to the silver melt soup and uniformly stirred by vacuum electromagnetic stirring. Mixing specific implementation to achieve uniform distribution of aluminum particles in the silver base, but other various aluminum-based particles (such as aluminum zirconium particles, aluminum zinc particles, aluminum-magnesium particles, aluminum copper particles, aluminum tin particles, and aluminum-bismuth particles, etc. Or common or innovative techniques for infiltrating aluminum metal into the silver wire can be used to practice the invention, for example, by plating an aluminum layer on the surface of the silver wire and then infiltrating the aluminum metal into the silver wire by heat treatment. (S1) implementation The segment is not limited; in addition, the particle size of the aluminum particles added is between 10 and 20 nm, and the amount of aluminum added is preferably between 3 wt.% and 8 wt.%; It is shown that the silver wire (20 μm) is doped (added) with nano aluminum particles of 0, 0.5 wt.%, 1 wt.%, 3 wt.%, 5 wt.%, 8 wt.%, and 10 wt.%, respectively. And the experimental data table of the melting current, tensile strength and ductility characteristics of the silver-based two-phase line obtained after the completion of the second step (S2) and the third step (S3) of the present invention; it can be clearly understood that the nano aluminum particles When the amount of addition is up to 8wt.%, the melting current of the silver-based two-phase line will be significantly lowered, and the silver-based two-phase line with the amount of aluminum added between 3wt.% and 8wt.% has the above three characteristics. Better average performance;

Step 2 (S2): Next, a surface of the silver base is plated with a chromium layer having a thickness of not less than 32 nm, thereby increasing the oxidation resistance of the silver base surface; wherein the thickness of the chromium layer is preferably between 32 nm and 106 nm. And step 3 (S3): heat-treating the silver-plated base of the chromium layer to cause the chromium ions of the chromium layer to enter the silver baseline base, and forming an anti-oxidation layer on the surface of the silver base, wherein the anti-oxidation layer contains A combination of one or both of an Ag ₂ Cr phase or an AgAl ₇ Cr phase is formed as a silver-based two-phase line; notably, the Ag ₂ Cr phase is preferably formed on the surface of the oxidation resistant layer, and AgAl ₇ Preferably, the Cr phase is formed inside the oxidation resistant layer; in addition, the heat treatment of the third step (S3) is heated to a temperature of 400 to 700 ° C and continues for no more than 1 hour; It is doped (added) with a silver base (20 μm) of 3 wt.%, 5 wt.%, and 8 wt.% of nano aluminum particles, respectively, and plated with 32 nm, 77 nm, and 106 nm chromium layers, respectively. Inventive Step 3 (S3) after completion of the different silver-based two-phase line in 7 days of atmospheric oxidation test, 24hr-12 0 °C high temperature oxidation test and heat treatment (480 ° C -25 min) after the high temperature oxidation test experimental data table; it can be clearly seen that the thickness of the chromium layer must be at least 32 nm, can be surface heat treated to form Ag ₂ Cr phase and AgAl ₇ Cr, to improve the oxidation resistance and thermal stability of the silver-based two-phase line, and when the thickness of the chromium layer exceeds 106 nm, the ductile difference between the hard chromium layer and the soft silver-based two-phase line is too large, so that the surface is easy to be drawn during the drawing process. Cracks are generated, and the thickness of the chrome layer is relatively high, which also increases the process cost.

Referring again to the table below, the above table is plated with 32nm, 77nm, and 106nm chromium layer of silver-based two-phase line (20μm) under heat treatment conditions (480 ° C -25 min) and (630 ° C -25 min) After the wire is formed into a ball, the experimental data table for the wire bonding (EFO), the wire bonding strength (gf), the wire contact breakdown voltage (v), and the interface intermetallic compound thickness are measured; it is obvious that When the temperature of the heat treatment is higher, the thinner the chromium layer remaining in the silver-based two-phase line, the thickness of the intermetallic compound in the wire bonding interface can be effectively suppressed, that is, the interface compound does not induce rapid growth in a high heat environment. The silver-based two-phase wire of the invention can have the effect of maintaining the low resistance characteristic of the circuit; in addition, the sphericity (roundness) and the wire bonding strength also meet the package wire quality requirements of the electronic industry parts; The tensile strength and the high temperature (120 ° C) tensile strength test, it can be seen that the electrothermal silver-based biphasic line of the present invention has an average of about 6 gf, and the normal silver alloy wire has a tensile strength of about 3 to 5 gf at room temperature. And almost no high temperature tensile strength, Compared with the comparison of 1gf, there is a considerable difference; it is worth noting that the thickness of the chromium layer after heat treatment of the electrothermal silver-based two-phase line of the present invention is preferably between 0 and 71 nm, that is, the chromium layer. The chromium ions can enter the silver-based two-phase line base completely or partially, so that the silver-based two-phase line can produce two structural forms due to the heat treatment conditions, one of which includes a silver baseline and an anti-oxidation layer surrounding the silver baseline surface. The silver base has no more than 8 wt.% of nano aluminum particles, and the oxidation resistant layer comprises one or a combination of Ag ₂ Cr phase or AgAl ₇ Cr phase, please refer to the second figure, which is the present invention. The silver base of one embodiment is after heat treatment, the silver baseline surface only has a microscopic organization chart of the anti-oxidation layer; and the other electrothermal silver-based biphasic line includes a silver base line and an anti-oxidation layer surrounding the silver baseline surface. And a chrome layer surrounding the surface of the anti-oxidation layer, as shown in the third figure, the silver baseline of the second embodiment of the present invention has a microstructure of the anti-oxidation layer and the chromium layer on the surface of the silver after heat treatment.

It can be seen from the above description that the present invention has the following advantages compared with the prior art:

1. The present invention by doping (adding) nano-pure aluminum particles into the silver wire, so that it is evenly distributed in the base, not only can increase the strength of the silver base line, but also maintain ductility; in addition, by chrome plating in silver The surface of the base layer is heat-treated to form Ag ₂ Cr and AgAl ₇ Cr phases, which can improve the oxidation resistance and avoid the problems caused by photothermal degradation or yellowing of the epoxy resin material used for sealing the bonding wires. The silver-based two-phase line has no abnormal coarse grains inside, and also improves the thermal stability of the silver-based two-phase line of the present invention.

2. The present invention controls the residual chrome plating layer by appropriate heat treatment conditions, so that the thickness of the interface intermetallic compound (for example, Ag ₂ Al or Ag ₄ Al) can be effectively suppressed after the wire is formed into a ball, thereby maintaining the silver-based two-phase line circuit. Low resistance characteristics.

In summary, the electrothermal silver-based dual-phase line of the present invention and the method for manufacturing the same can achieve the intended use efficiency by the above-disclosed embodiments, and the present invention has not been disclosed before the application. Full compliance with the requirements and requirements of the Patent Law.提出Apply for an invention patent in accordance with the law, please submit a review and grant a patent. It is really sensible.

The illustrations and descriptions of the present invention are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; those skilled in the art, which are characterized by the scope of the present invention, Equivalent variations or modifications are considered to be within the scope of the design of the invention.

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(S2)‧‧‧Step 2

(S3) ‧ ‧ Step 3

Claims (8)

The invention relates to a method for manufacturing an electrothermal-resistant silver-based two-phase line, comprising the following steps: Step 1: forming aluminum particles of not more than 8 wt.% in a silver wire, and uniformly distributing the aluminum particles in a silver base. The silver wire is formed as a silver baseline; step 2: depositing a chromium layer having a thickness of not less than 32 nm on the surface of the silver base; and step 3: heat treating the silver base plated with the chromium layer to make the chromium a layer of chromium ions enters the silver baseline base, and an anti-oxidation layer is formed on the surface of the silver base, wherein the oxidation resistant layer comprises one or a combination of Ag ₂ Cr phase or AgAl ₇ Cr phase, ie, For a silver-based two-phase line, the heat treatment is carried out to a temperature of 400 to 700 ° C and the temperature is continued for no more than 1 hour. The method for manufacturing an electrothermal-resistant silver-based two-phase line according to claim 1, wherein the step of adding the aluminum particles to the silver melt is stirred and uniformly mixed. The method for manufacturing an electrothermal-resistant silver-based two-phase line according to the first aspect of the invention, wherein the aluminum particles have a particle diameter of between 10 and 20 nm. The method for manufacturing an electrothermal-resistant silver-based two-phase line according to claim 1, wherein the step is to add 3 wt.% to 8 wt.% of aluminum particles. The method for manufacturing an electrothermal-resistant silver-based two-phase wire according to claim 1, wherein the chromium layer has a thickness of between 32 nm and 106 nm. The manufacturer of the electrothermal silver-based two-phase line as described in claim 6 of the patent application scope The method, wherein the third step is to make the chromium ion of the chromium layer completely or partially enter the silver baseline base. An electrothermally resistant silver-based biphasic line comprising a silver baseline and an oxidation resistant layer surrounding the silver baseline surface, the silver baseline having no more than 8 wt.% aluminum particles, and the oxidation resistant layer comprising Ag ₂ Cr phase Or one of or a combination of AgAl ₇ Cr phases. An electrothermally resistant silver-based biphasic line comprising a silver base, an oxidation resistant layer surrounding the silver baseline surface, and a chromium layer surrounding the surface of the oxidation resistant layer, the silver baseline having no more than 8 wt.% aluminum particles And the oxidation resistant layer comprises one or a combination of an Ag ₂ Cr phase or an AgAl ₇ Cr phase.