KR101447505B1 - Solder joint structure having tooth-like structure with excellent efficiency for suppressing the formation of kirkendall voids and method of manufacturing the same - Google Patents

Abstract

A solder joint structure having a tooth structure excellent in the effect of inhibiting the formation of a curcaldoid void by performing a soldering process after forming a copper-nickel tooth tissue layer using a direct current electrolytic plating method, and a method of manufacturing the same.
A solder joint structure having a tooth structure according to an embodiment of the present invention includes a copper-nickel dental tissue layer constituting a pad of a substrate; A solder connected on the copper-nickel tooth tissue layer; And an intermetallic compound layer formed at an interface between the copper-nickel tooth tissue layer and the solder and inhibiting the generation of a Kirkendall void, wherein the copper-nickel tooth tissue layer comprises copper (Cu): 50 to 65 By weight and nickel (Ni): 35 to 50% by weight.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder joint structure having a tooth structure excellent in suppressing the formation of a cupolaoid void and a method of manufacturing the solder joint structure.

The present invention relates to a solder joint structure having a tooth structure and a manufacturing method thereof, and more particularly, to a solder joint structure having a tooth structure, and more particularly, to a solder joint structure having a tooth structure, ) And a method of manufacturing the same.

In general, the connection method of reflowing solder balls or solder paste onto a copper layer is most commonly utilized in surface mount technology (SMT). However, when solder balls or solder paste are soldered onto the copper layer, Kirkendall voids are formed by the formation of an intermetallic compound layer having an epsilon-phase Cu ₃ Sn structure at the interface between the copper layer and the solder at a sufficient solid- Is generated.

Since such a keel-bonded void grows in a mutually interconnected manner, the reliability of the mechanical impact characteristic at the solder joint, which is a joint portion between the copper layer and the solder, is adversely affected.

In particular, it is common to perform copper plating in a high-density substrate or printed circuit board industry, and to form copper microcircuits on a substrate or printed circuit board (PCB) by a semi-additive or permanent method. The reliability of the joints due to the curtain wall void can become increasingly widespread in the future. Therefore, in recent years, researches on electrolytic plating methods for suppressing the formation of such a curtain-like void have been actively conducted.

Conventional studies have shown that when a solder joint structure is formed using a copper-zinc alloy layer, the growth of the intermetallic compound at the interface between the lead-free solder and the copper layer and the growth of the interconnected voids in the intermetallic compound are suppressed It has been reported successful. However, the solder joint structure using such a copper-zinc alloy layer still has problems such as reduced wettability and galvanic corrosion. Moreover, zinc is considered a material that is not commonly used in high density substrates or in the printed circuit board industry.

A related prior art is Korean Patent No. 10-0474207 (published on Mar. 11, 2005), which discloses an air pad solder bonding structure of a wafer level package and a manufacturing method thereof.

An object of the present invention is to provide a solder joint structure and a solder joint structure excellent in the effect of inhibiting the formation of ketaldal voids capable of inhibiting the formation of a kenderald void at a solder joint region during solid phase aging by producing a copper- And a manufacturing method thereof.

According to an aspect of the present invention, there is provided a solder joint structure having a tooth structure, comprising: a copper-nickel dental tissue layer constituting a pad of a substrate; A solder connected on the copper-nickel tooth tissue layer; And an intermetallic compound layer formed at an interface between the copper-nickel tooth tissue layer and the solder and inhibiting the generation of a Kirkendall void, wherein the copper-nickel tooth tissue layer comprises copper (Cu): 50 to 65 By weight and nickel (Ni): 35 to 50% by weight.

According to another aspect of the present invention, there is provided a method of manufacturing a solder joint structure having tooth structures, comprising: (a) immersing a substrate having a pad in an electrolytic plating bath filled with a plating solution; (b) Direct current electrolytic plating is performed on the pads of the substrate immersed in the electrolytic plating bath at a current density of 0.025 to 0.055 A / dm ² to produce copper (Cu): 50 to 65 wt% and nickel (Ni): 35 to 50 Forming a copper-nickel tooth tissue layer constituted by weight%; And (c) subjecting the solder to the copper-nickel tooth tissue layer and then performing a reflow treatment to connect the solder to the copper-nickel tooth tissue layer.

The solder joint structure having a tooth structure and the method of manufacturing the same according to the present invention can be manufactured by directly electroplating at a current density of 0.025 to 0.055 A / dm ² , which is comparatively low, to 50 to 65 wt% of copper (Cu) Ni): 35 to 50% by weight based on the total weight of the copper-nickel tooth tissue layer. Therefore, if the copper-nickel tooth structure layer having the above composition is connected to a solder ball or a solder paste used for electronic component mounting by a soldering process, generation of a keelkond void can be suppressed even during long-term use, thereby improving the mechanical bonding reliability of the solder joint There is an advantage.

1 is a view illustrating a structure of a solder joint having a tooth structure according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a structure of a solder joint having a tooth structure according to an embodiment of the present invention.
3 is a schematic view for explaining a DC electrolytic plating method.
FIG. 4 is a photograph of the surface of a copper-nickel tooth tissue layer formed after electroplating for 1 hour according to a change in current density, taken by optical micrographs.
5 is a photograph of a surface of a copper-nickel tooth tissue layer formed after electroplating for 1 hour according to a change in current density, by SEM (scanning electron micrographs).
FIG. 6 is a photograph of a cut surface of a copper-nickel tooth tissue layer formed after electrolytic plating for one hour in accordance with a change in current density, by an optical microscope.
7 shows the thickness of the copper-nickel tooth tissue layer measured according to the change of the current density and the electroplating time.
FIG. 8 shows the composition ratio of the copper-nickel tooth tissue layer measured after performing electrolytic plating for 1 hour in accordance with the change of the current density.
9 is a SEM photograph of a cut surface of a copper-nickel tooth tissue layer at a local position after electrolytic plating for 1 hour at a current density of 0.06 A / dm ² .
10 shows the results of EDS measurement at points A and B in FIG.
FIG. 11 is a SEM photograph of the cross section of the intermetallic compound layer grown at the interface between the Cu layer and the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball after aging at 125 ° C (b) after aging for 480 hours with Cu-Ni tooth tissue layer, (c) after 720 hours aging with Cu-Ni tooth tissue layer.
FIG. 12 is an EPMA mapping image of a cross section of the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball after aging at 125 ° C. for 480 hours Lt; / RTI >
FIG. 13 is an EPMA mapping image of a cross section of the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer and Sn-3.0 wt% Ag-0.5 wt% Cu solder balls after aging at 125 ° C for 720 hours Lt; / RTI >
14 is a schematic diagram showing the reaction at the interface between the Cu layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball before and after the aging treatment for the intermetallic compound layer grown at the interface.
FIG. 15 is a schematic diagram showing the reaction at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball before and after the aging treatment for the intermetallic compound layer grown at the interface.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solder joint structure having a tooth structure according to a preferred embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing a solder joint structure having tooth structure according to an embodiment of the present invention.

Referring to FIG. 1, a structure 100 of a solder joint having a tooth structure according to an embodiment of the present invention includes a copper-nickel tooth tissue layer 120, a solder ball 140, and an intermetallic compound layer 160. When the solder ball 140 is replaced with solder paste and reflowed, the same structure can be considered.

A copper-nickel tooth tissue layer 120 is formed on a pad (not shown) of the substrate. Preferably, the copper-nickel tooth tissue layer 120 includes 50 to 65% by weight of copper (Cu) and 35 to 50% by weight of nickel (Ni). In this case, when the composition ratio of the copper-nickel tooth tissue layer 120 is realized while having the tooth structure in the above-mentioned range, the reliability of bonding with the solder ball to be described later is excellent, so that the generation of the curtain- And the mechanical bonding reliability of the test piece is greatly improved.

Solder ball 140 is connected on copper-nickel tooth tissue layer 120. The solder ball 140 may include 2.5 to 3.5% by weight of silver (Ag), 0.1 to 1.0% by weight of copper (Cu), and the balance tin (Sn). This solder ball 140 is connected on the copper-nickel tooth tissue layer 120 by applying flux and reflowing it.

The intermetallic compound 160 is formed at the interface between the copper-nickel dental tissue layer 120 and the solder ball 140 and serves to bond the solder ball 140 and the copper-nickel dental tissue layer 120 together. The intermetallic compound layer 160 includes a first layer 160a formed in the upper region adjacent to the solder ball 140 and a second layer 160b formed in the lower region adjacent to the copper- . Here, the upper region may include a surface, and the lower region may be defined to include a bottom surface. At this time, the first layer 160a has a composition of (Cu, Ni) ₆ Sn ₅ , and the second layer 160b has a composition of (Ni, Cu) ₃ Sn ₄ .

In the conventional case, in the case of the intermetallic compound layer formed at the interface between the pure copper layer and the solder ball, the Cu ₆ Sn ₅ layer and the Cu ₃ Sn layer were generated. Especially, in the solid-state aging condition in which the solder ball was heated under the solid state, The Cu ₃ Sn layer is reported to form a curtain wall void. In contrast, the present invention copper of dental tissues suggested in - in this case to apply the nickel layer (Cu, Ni) in a spot produced Cu ₆ Sn ₅ layer in the solid state aging conditions ₆ Sn ₅ layer, Cu ₃ Sn layer forming spot (Ni, Cu) ₃ Sn ₄ layer is formed and consequently the formation of the curcendoloid is suppressed.

Hereinafter, a method of manufacturing a solder joint structure having a tooth structure according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a flowchart illustrating a method of manufacturing a solder joint structure having a tooth structure according to an embodiment of the present invention.

Referring to FIG. 2, the manufacturing method of the solder joint structure having the tooth structure shown includes an immersion step (S210), a copper-nickel tooth layer formation step (S220), and a solder joint formation step (S230).

Immersion

In the immersion step (S210), the substrate having the pad is immersed in an electrolytic plating bath filled with the plating liquid.

At this time, the pH of the plating solution is preferably maintained at 8 to 10. When the pH of the plating solution is less than 8 or more than 10, the gloss of the plating layer is lowered, and the problem of non-uniform gloss may occur.

The pH of the plating solution is preferably adjusted with an aqueous ammonia solution.

Copper-nickel tooth layer formation

In the copper-nickel tooth layer formation step (S220), a copper-nickel tooth tissue layer is formed by DC electroplating at a current density of 0.025 to 0.055 A / dm ² on the pad of the substrate immersed in the electrolytic plating bath.

The inventors of the present invention have found that DC electrolytic plating is performed to improve the plating speed, and a copper-nickel tooth tissue layer having a tooth structure is formed. Particularly, since the copper-nickel tooth structure layer having a tooth structure manufactured by the direct current electrolytic plating method is gradually changed into a uniform copper-nickel alloy structure in the solid phase aging process to be described later, the tooth structure immediately after plating is excellent in long- I can not influence it.

At this time, it is preferable that the copper-nickel tooth tissue layer contains 50 to 65 wt% of copper (Cu) and 35 to 50 wt% of nickel (Ni). In this case, when the composition ratio of the copper-nickel tooth tissue layer is added in the above-mentioned range, it has a tooth structure and is excellent in reliability of bonding with solder to be described later, so that generation of the curcurate void is suppressed during long- It is confirmed through experiments that the reliability is greatly improved.

In particular, it has been experimentally found that when the current density is applied in the range of 0.025 to 0.055 A / dm ² , the final composition ratio of the copper-nickel tooth tissue layer formed by the deposition is in the above range and the microstructure of the micro- Respectively.

Solder joint formation

In the solder joint forming step S230, lead-free solder is reflowed on the copper-nickel tooth structure layer to form a joint. The lead-free solder may include 2.5 to 3.5% by weight of silver (Ag), 0.1 to 1.0% by weight of copper (Cu), and the remaining tin (Sn).

In this step, an intermetallic compound is formed at the interface between the copper-nickel tooth tissue layer and the solder material.

The intermetallic compound layer may include a first layer formed in the upper region adjacent to the solder ball through solid-phase aging and a second layer formed in the lower region adjacent to the copper-nickel tooth tissue layer. At this time, the first layer has a composition of (Cu, Ni) ₆ Sn ₅ , and the second layer has a composition of (Ni, Cu) ₃ Sn ₄ .

In the conventional case, in the case of the intermetallic compound layer formed at the interface between the pure copper layer and the solder ball, the Cu ₆ Sn ₅ layer and the Cu ₃ Sn layer were generated. Especially, in the solid-state aging condition in which the solder ball was heated under the solid state, The Cu ₃ Sn layer is reported to form a curtain wall void. In contrast, the present invention copper of dental tissues suggested in - in this case to apply the nickel layer (Cu, Ni) in a spot produced Cu ₆ Sn ₅ layer in the solid state aging conditions ₆ Sn ₅ layer, Cu ₃ Sn layer forming spot (Ni, Cu) ₃ Sn ₄ layer is formed and consequently the formation of the curcendoloid is suppressed.

In the solder bonding structure having the tooth tissue layers to be produced by the above process (S210 ~ S230) of copper-nickel dental tissue layers using a composite plating solution containing copper and nickel ions is relatively low 0.025 to current density of 0.055 A / dm ² And a copper-nickel tooth tissue layer composed of copper (Cu) in an amount of 50 to 65 wt% and nickel (Ni) in an amount of 35 to 50 wt% can be produced. Therefore, when the copper-nickel tooth structure layer having the above composition is connected to the solder material used for electronic component mounting by a soldering process, the generation of the keelkond void during the long-term use can be suppressed and the mechanical bonding reliability of the solder joint can be improved have.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Experimental method

FIG. 3 is a schematic view for explaining the DC electrolytic plating method, which will be described with reference to FIG.

The plating solution contained nickel (II) sulfate hexahydrate, NiSO ₄ .6H ₂ O, 98.5%, 0.475 M, copper (II) sulfate pentahydrate, CuSO ₄ H ₂ O, 0.125 M}, and sodium citrate tribasic dehydrate (Na ₃ C ₆ H ₅ O ₇ .2H ₂ O, 99%, 0.20 M} were used.

At this time, the pH of the plating solution filled in the electrolytic plating bath was adjusted to 9.0 using an aqueous ammonia solution (28 to 30%), and the direct current electrolytic plating was performed at room temperature.

The substrate used was a 3N Cu plate with a width of 20 mm × 20 mm × 1 mm, and a Ni mesh was used as the cathode.

In this case, the substrate and the negative electrode cross the liver sikyeotgo held to be spaced apart at an interval of 30mm, the current density of the electrolytic direct current plating under the condition of ^{0.04 A / dm 2, 0.05 A} / dm 2, 0.06 A / dm 2, 0.07 A / dm 2 Respectively.

To measure the deposition thickness with plating time, the electroplated specimens were removed from the plating bath at 15 minute intervals.

On the other hand, the microstructure and thickness of the electroplated Cu-Ni dental tissue layer were observed using optical microscopies (OM) and scanning electron microscopes (SEM), respectively. The component analysis of the electroplated plated layers was performed using energy dispersive spectroscopy (EDS).

Then, in the plating layers subjected to electrolytic plating under each condition, an upper portion excluding a circular shape portion having a diameter of 1.5 mm was coated with solder resist and cured to form a circular pad. Finally, 14 Sn-3.0 wt% Ag-0.5 Cu solder balls having a diameter of 450 mu m mixed with a water-soluble flux (WF6063M, Senju Metal) were reflowed and connected to copper-nickel tooth tissue layer pads. After the reflow treatment, solid phase aging treatment was carried out at 125 캜.

Sections of the solder joint structure including the copper-nickel plated layer and solder balls were analyzed by SEM. In order to obtain a clear SEM image of the interface between the copper-nickel layer and the solder ball, the cut surfaces of the copper-nickel tooth tissue layer and the solder ball were etched with a mixed solution of 4 vol% of CH ₃ OH, 1 vol% of HNO ₃ and HCl.

2. Microstructure Observation

FIG. 4 is a photograph of the surface of a copper-nickel tooth tissue layer formed after electroplating for 1 hour according to a change in current density, taken by optical micrographs.

As shown in FIG. 4, a specimen manufactured under a current density condition of 0.04 A / dm ² has a flat surface morphology, whereas a specimen manufactured under a current density condition of 0.05 A / dm ² has a surface partially It can be confirmed that it is rough. In addition, the specimens prepared at current density of 0.06 A / dm ² showed a rapid increase in irregular micro nodules. Finally, the specimens prepared under current density conditions of 0.07 A / dm ² did not increase the nodule size, but the amount of nodule was further increased.

In summary, as the current density increases, the deposition surface of the copper and nickel atoms changes from a flat shape to a spherical nodule surface, and as a result, the surface morphology becomes rough.

Such roughness can cause micro voids due to pore formation during flux application during subsequent soldering processes. Therefore, current densities of 0.06 and 0.07 A / dm < ² > are considered to be inadequate process conditions.

5 is a photograph of a surface of a copper-nickel tooth tissue layer formed after electroplating for 1 hour according to a change in current density, by SEM (scanning electron micrographs).

As can be seen from the high magnification SEM image, the specimen produced at the current density condition of 0.04 A / dm ² , as shown in Figure 5 (a), shows that the high magnification surface is still relatively smooth.

On the other hand, as shown in FIG. 5 (b), the specimen produced at the current density condition of 0.05 A / dm ² partially had some fine surface defects such as pin holes.

Based on the results shown and described in FIGS. 4 and 5, it was confirmed that the surface morphology of the copper-nickel tooth structure fabricated under the current density condition of 0.04 A / dm ² is most suitable as a pad for the subsequent soldering process. However, the copper-nickel tooth tissue layer produced at a current density of 0.05 A / dm ² is also suitable for subsequent soldering processes.

FIG. 6 is a photograph of a cut surface of a copper-nickel tooth tissue layer formed after electrolytic plating for one hour in accordance with a change in current density by an optical microscope.

A, 0.04 ~ 0.07 A / dm tooth tissue layers across the current density of ² as it is shown in (a) to (d) of Figure 6 were observed. It can be seen that as the current density increases, it has a generally slightly more pronounced tooth structure.

In other words, the dental tissue is a word in which the orange and green-gray columns are repeatedly arranged on an optical microscope image.

This implies that the co-deposition of copper and nickel atoms by the direct-current plating is deposited at a locally more concentrated concentration rather than at a completely uniform mixing ratio.

7 shows the thickness of the copper-nickel tooth tissue layer measured according to the change of the current density and the electroplating time.

As shown in FIG. 7, it is generally understood that the deposition thickness increases linearly with the increase of the deposition time. Also, it can be seen that as the current density increases, the deposition thickness also increases slightly.

FIG. 8 shows the composition ratio of the copper-nickel tooth tissue layer measured after performing electrolytic plating for 1 hour in accordance with the change of the current density.

As shown in FIG. 8, it can be seen that as the current density increases, the nickel average content in the copper-nickel tooth tissue layer linearly increases. Particularly, in the case of the current density condition of 0.04 A / dm ² which had the best surface form, the average composition ratio of the copper-alloy plating layer was 65 wt% of copper and 32.5 wt% of nickel.

FIG. 9 is a photograph of a section of the copper-nickel tooth tissue layer taken by SEM after electroplating at a current density of 0.06 A / dm ² for 1 hour, and FIG. 10 is a photograph taken at a local point of A and B of FIG. 9 EDS measurement results.

As shown in FIG. 9 and FIG. 10, it is evident that the composition detected at point A as a result of EDS measurement contains a relatively large amount of nickel, while the composition detected at point B contains a relatively large amount of copper Can be confirmed. It can be seen that all of the dental tissue layers shown in Fig. 6 have fine dental tissue phases partially containing copper or nickel in a large amount in all cases despite the average compositional change of the whole. An analysis of the plated tissue layer at a current density of 0.06 A / dm ² is an example of a dental tissue layer, and similar results can be obtained when analyzing a plated tissue layer at a current density of 0.04 A / dm ² have.

3. Investigation of the growth characteristics of intermetallic compound layer at the interface between solder and copper-nickel tooth structure during solid-state aging after reflow process

Table 1 shows the average thicknesses of intermetallic compound layers measured at solidification aging time at 125 ° C. At this time, the copper-nickel tooth tissue layer used as a pad was manufactured at an optimum condition of 0.04 A / dm ² current density.

[Table 1]

Referring to Table 1, it can be seen that the average thickness of the intermetallic compound layer also increases as the solid-phase aging time increases. It can be seen that the thickness of the intermetallic compound layer grown on the copper-nickel tooth tissue layer is slightly thinner than the thickness of the intermetallic compound layer grown on the copper plating layer, provided that all the experimental conditions are the same.

FIG. 11 is a SEM photograph of the cross section of the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer or Cu layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball after aging at 125 ° C to be.

As shown in Fig. 11 (a), the intermetallic compound layer formed after solid-phase aging for 240 hours on a pure copper layer produced by direct current electrolysis showed a typical scallop shape. Moreover, the keelendic voids resulting from the difference in the interdiffusion rates of tin and copper were also observed in the Cu ₃ Sn layer, which is the lower region of the intermetallic compound layer, after aging for 10 days (240 hours).

On the other hand, the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder ball observed immediately after the reflow process showed a needle shape, As shown, this shape was clearly observed until a solid aging treatment of 480 hours progressed. As shown in Fig. 11 (c), when the aging time approaches 720 hours, the surface morphology of the intermetallic compound layer becomes smooth.

Also, as shown in Fig. 11 (c), it was the most surprising finding that after the aging treatment for 720 hours, no keelkendall void was observed at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 Ag-0.5 Cu solder. On the contrary, in the case of pure copper layer as mentioned above, a keelendal void was formed even after the aging treatment for 240 hours.

In order to explain the mechanism of suppression of the formation of cupidal voids in the copper-nickel tooth tissue layer, it was found that the cut surface at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Were subjected to an EPMA mapping test.

12 shows the EPMA map of the cut surface of the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer and Sn-3.0 wt% Ag-0.5 w% Cu solder after aging treatment at 125 ° C for 480 hours .

As shown in Fig. 12, the distribution of copper and nickel elements in the copper-nickel tooth tissue layer is changed to a relatively uniform state when compared with the microstructures observed in Fig. This means that it is being transferred onto the equilibrium solid-solution by diffusion during the aging process.

The distribution of tin, copper and nickel elements in the intermetallic compound layer was measured. At this time, the distribution of copper and nickel in the intermetallic compound layer was observed to be very uniform.

However, it was observed that the thickness of the copper distribution measured in the intermetallic compound layer was somewhat thicker than that of the nickel distribution, and the concentration of tin in the intermetallic compound layer tended to decrease slightly toward the bottom of the intermetallic compound layer . These results indicate that the upper side of the intermetallic compound layer is a copper - based intermetallic compound and the lower side of the intermetallic compound layer is a nickel - based intermetallic compound.

13 shows an EPMA map of the cut surface of the intermetallic compound layer grown at the interface between the Cu-Ni tooth tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder after aging treatment at 125 DEG C for 720 hours .

As shown in Fig. 13, the copper-nickel tooth tissue layer showed a more uniformly mixed solid phase, and the thickness of the copper distribution measured in the intermetallic compound layer was apparently thicker than the nickel distribution thickness. It can also be seen that the concentration of tin in the intermetallic compound layer still decreases along the direction of the copper-nickel tooth tissue layer. These results indicate that the upper part of the intermetallic compound layer is a copper - based intermetallic compound and the lower part of the intermetallic compound layer is sufficiently transferred to a nickel - based intermetallic compound.

14 is a graphical representation of the interfacial reaction before and after solid-phase aging treatment for the intermetallic compound layer grown at the interface between a general Cu layer and a Sn-3.0 wt% Ag-0.5 wt% Cu solder, FIG. 5 is a diagrammatic representation of the interfacial reaction before and after solid-phase aging for the intermetallic compound layer grown at the interface between the Ni dental tissue layer and the Sn-3.0 wt% Ag-0.5 wt% Cu solder.

As shown in Fig. 15, due to the faster diffusion rate of copper compared to nickel in the direction of the upper solder, the lower region of the intermetallic compound layer changes to an intermetallic compound layer containing a large amount of nickel during the solid- It can be seen that the upper region of the compound layer gradually changes to an intermetallic compound containing a relatively large amount of copper.

As a result, the upper region of the intermetallic compound layer is transferred to (Cu _x , Ni _1-x ) ₆ Sn ₅ phase and the lower region is transferred to (Ni _y , Cu _1-y ) ₃ Sn ₄ phase.

On the other hand, as shown in Fig. 14, during the solid-phase aging in the normal Cu layer, the Cu dissipation rate of the Cu layer to the solder is faster than the diffusion rate of the tin-based solder component into the Cu layer, and in the interface between the adjacent Cu ₃ Sn layer of the copper layer of Cu ₆ Sn ₅ layer and the Cu ₃ Sn layer formed between the Cu layer increases to produce a void Kendall.

Referring again to FIG. 15, nickel atoms having a lower diffusion rate relative to copper are deposited in the bottom region of the Cu-Ni-Sn intermetallic compound layer formed immediately after reflow, that is, Cu-Ni dental tissue layer and Sn-3.0 wt% There is a high possibility that the Cu-Ni-Sn intermetallic compound layer present at the interface of the Ag-0.5 wt% Cu solder exists in the region adjacent to the copper-nickel tooth tissue layer. Therefore, this cause can be regarded as an important reason for suppressing the formation of keelendal voids. In short, as a result of the above phenomenon, the intermetallic compound observed in the bottom region of the Cu-Ni-Sn intermetallic compound layer after aging exists in the composition of Ni and Sn-based intermetallic compound, ie, (Ni, Cu) ₃ Sn ₄ do.

Since the intermetallic compound phase having an Ni- and Sn-based phase has a smaller volume shrinkage phenomenon than the intermetallic compound phase having a phase based on Cu and Sn, the surface cracking defect in the solder joint portion due to external impact Can be reduced.

Therefore, solder joints using pads made of Cu-Ni dental tissue layer can exhibit more excellent reliability due to falling, impact and vibration compared to solder joints made of conventional Cu pads.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

100: solder joint structure 120: copper-nickel tooth layer
140: solder ball 160: intermetallic compound layer
160a: first layer of an intermetallic compound layer 160b: second layer of an intermetallic compound layer
S210: Immersion step
S220: Copper-nickel tooth layer formation step
S230: Solder joint formation step

Claims (5)

A copper-nickel dental tissue layer constituting pads of a substrate and arranged in a columnar shape repeatedly;
A solder connected on the copper-nickel tooth tissue layer; And
An intermetallic compound layer formed at an interface between the copper-nickel tooth tissue layer and the solder and inhibiting the formation of a Kirkendall void,
Wherein the copper-nickel dental tissue layer comprises 50 to 65 wt% of copper (Cu) and 35 to 50 wt% of nickel (Ni).
The method according to claim 1,
The solder
Wherein the copper-nickel layer has a tin-based composition comprising 2.5 to 3.5% by weight of silver (Ag), 0.1 to 1.0% by weight of copper (Cu) .
The method according to claim 1,
After the solid phase aging
The upper region adjacent to the solder has a composition of (Cu, Ni) ₆ Sn ₅ ,
Wherein the lower region adjacent to the copper-nickel tooth tissue layer has a composition of (Ni, Cu) ₃ Sn ₄ .
(a) immersing a substrate having a pad in an electrolytic plating bath filled with a plating solution;
(b) Direct current electrolytic plating is performed on the pads of the substrate immersed in the electrolytic plating bath at a current density of 0.04 to 0.05 A / dm ² to produce copper (Cu): 50 to 65 wt% and nickel (Ni): 35 to 50 Forming a copper-nickel tooth tissue layer constituted by weight%; And
(c) contacting the solder on the copper-nickel tooth tissue layer and then reflowing the copper-nickel tooth tissue layer to connect the solder to the copper-nickel tooth tissue layer. Wherein the solder joint structure is formed on the substrate.
5. The method of claim 4,
In the step (c)
At the interface between the copper-nickel tooth tissue layer and the solder
Wherein an intermetallic compound layer having a property of inhibiting the formation of a Kirkendall void is formed on the surface of the dental tissue copper-nickel layer.

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