KR102040280B1 - Lead-free solder composition and manufacturing method of the same, bonding method using lead-free solder composition - Google Patents

Abstract

A solder containing Sn; And an additive added to the solder, wherein the additive comprises a carbon structure; And a coating layer of a metal material positioned on the surface of the carbon structure, wherein the lead-free solder alloy composition including at least one of Ag, Ni, Pt, and Pd is introduced.

Description

LEAD-FREE SOLDER COMPOSITION AND MANUFACTURING METHOD OF THE SAME, BONDING METHOD USING LEAD-FREE SOLDER COMPOSITION}

The present invention relates to a lead-free solder alloy composition and a method of manufacturing the same.

Specifically, the lead-free solder alloy composition having no toxicity and minimizing the effect of harmful metal elements on the environment by solving environmental problems caused by the toxicity of lead (Pb), and having excellent solderability, mechanical properties and thermal conductivity And to a method for producing the same.

When disposing of electronic devices using flexible solder, lead (Pb) component contained in solder is eluted by acid rain, which contaminates groundwater. If it is absorbed by human body, it is pointed out as environmental pollutant that harms human body such as reduced intelligence and reduced reproduction function. Sn-Pb solder has been replaced by lead-free solder.

Techniques related to such lead-free solders have been proposed in KR 1998-0023274 A and KR 10-0797161 B1.

The lead-free solder composition of KR 1998-0023274 A is a lead-free solder composition composed of tin (Sn), silver (Ag), bismuth (Bi), and indium (In), wherein the tin (Sn) is 82 to 93wt%, silver ( Ag) is 2wt%, bismuth (Bi) is 3 ~ 10wt%, Indium (In) is prepared by mixing 2 ~ 6wt%.

However, the indium (In) required to implement the lead-free solder composition according to KR 1998-0023274 A is expensive, and the solder containing bismuth (Bi) is brittle due to the increase in the bismuth (Bi) content causing brittleness There is this.

The lead-free solder composition of KR 10-0797161 B1 is a lead-free solder composition composed of tin (Sn), silver (Ag), and indium (In), and has a content of 0.3 wt% or more and less than 2.5 wt% silver (Ag), 0.1 wt%. A tin-silver-copper-indium quaternary lead-free solder composition comprising at least 2 wt% copper (Cu), at least 0.1 wt% and at most 1.2 wt% indium (In), and the remainder being tin (Sn). However, KR 10-0797161 B1 also uses expensive indium (In) to implement the pyrometer lead-free solder composition, it is not suitable for general applications in the industry.

On the other hand, in research and development of lead-free solders containing elements such as Sn, Ag, Bi, Cu, In, Zn, and the like, in particular, interest in compositions containing Sn, Ag, Cu is increasing.

However, the above-mentioned lead-free solders each have disadvantages. Zn, for example, is sensitive to oxidation and consequent decreases in solderability. Solder containing Bi is ductile and decreases with increasing Bi content, causing brittleness. Sn-Cu solder is inexpensive but poor in wettability, and is easy to form Ag3Sn, which is a coarse needle-like intermetallic compound, in solders containing Ag, deteriorating solderability and lowering strength. In conclusion, the development of lead-free solders requires minimizing the aforementioned disadvantages.

Among lead-free solders, Sn-0.7% Cu, Sn-3.5% Ag, 96.5wt% Sn-3.0wt% Ag-0.5wt% Cu, and their microstructures are dendritic, β-Sn, and Ag3Sn. And a process phase composed of Cu ₆ Sn ₅ . Since Ag ₃ Sn and Cu ₆ Sn ₅ intermetallic compounds (IMC) play a role of increasing the strength of the matrix, it is preferable that Ag ₃ Sn and Cu ₆ Sn ₅ are in an appropriate amount and in the Sn matrix. However, when Ag ₃ Sn and Cu ₆ Sn ₅ are too large or too large, the brittleness of the Sn-based solder is increased, thereby decreasing the strength. Usually, the content of Ag is 4.5% or less, and the content of Cu is 1% or less.

In addition, when the Ag content is more than 2wt% in the Sn solder matrix, coarse plate shapes of Ag ₃ Sn are likely to occur. That is, Sn, Ag ₃ Sn, and Cu ₆ Sn ₅ having large particle sizes lower the strength. This deteriorates the solderability and lowers the strength. On the other hand, if the content of Ag in the Sn-Ag alloy is less than 2wt%, this increases the liquidus temperature, increases the liquid phase + solid phase coexistence area and reduces the strength of the joint.

At present, the most commonly used Sn-based lead-free solder in consideration of melting point, bonding property, reliability, and the like is Ag content of 3 to 3.5% and Cu content of 0.5 to 0.7%. In this case, there is a disadvantage in that coarse platelets of Ag 3 Sn are easily generated with a relatively high Ag content. In order to solve this disadvantage, coarse Ag ₃ Sn needs to be refined, and in this process, Sn base metal grains can also be refined to further improve solder performance.

As a method for this, it is necessary to include the particle refining material in the solder composition, and such materials include metal powders such as aluminum (Al), nickel (Ni), silver (Ag), copper (Cu), and the like. However, metal powder materials have a disadvantage in that oxidation becomes easier when the particle size becomes smaller.

In order to solve the above problems of the metal powder material, ceramic powders such as aluminum nitride (AlN), yttrium oxide (Y ₂ O ₃ ), silicon carbide (SiC), and the like are present. Such ceramic powder material has the advantage of miniaturizing the particles and stable at high temperature to strengthen the solder. However, the ceramic powder material is brittle, and there is a difference between the known Sn metal and the crystal lattice, so that when the solder is loaded, the ceramic powder material itself is destroyed, or a crack is generated at the ceramic powder material and the Sn metal interface to increase the strength. There is a disadvantage of deterioration. In addition, the ceramic powder does not have good wettability, and has a disadvantage in that the powder is agglomerated at the manufacture of the ceramic nanocomposite solder alloy, or is not well mixed with a known Sn metal.

Therefore, in order to solve the above problems, there is a need for a nano composite lead-free solder using a carbon structure, such as graphene, carbon nanotubes, fullerenes, graphite nanomaterials.

An object of the present invention is non-toxic, by solving the environmental problems caused by the toxicity of lead (Pb) can minimize the impact of harmful metal elements on the environment, lead-free having excellent solderability, mechanical properties and thermal conductivity It is to provide a solder alloy composition and a method of manufacturing the same.

A lead-free solder alloy composition according to an embodiment of the present invention is a solder containing Sn; And an additive added to the solder, wherein the additive comprises: a carbon structure; And a coating layer of a metal material positioned on the surface of the carbon structure, wherein the metal includes at least one of Ag, Ni, Pt, and Pd.

The solder may further include one or more of Ag, Cu, Zn, Ni, and Sb.

The carbon structure may include at least one of graphene, graphite, graphite, carbon nanotubes, and fullerenes.

The coating layer may have a concave-convex structure in which convex portions and concave portions are irregularly repeated on a surface thereof.

The coating layer may have an average thickness of 20 to 500 kPa.

The additive may include more than 0.01% and less than 5.0% based on 100% of the total weight.

The additive, the average grain size may be 1nm to 100㎛.

Lead-free solder alloy composition manufacturing method according to an embodiment of the present invention comprises the steps of preparing an additive by forming a coating layer of a metal material on the surface of the carbon structure; Melting a solder containing Sn; And mixing the additive and the molten solder, followed by stirring, wherein the metal includes at least one of Ag, Ni, Pt, and Pd.

Before preparing the additive, the carbon structure may be pulverized to form the carbon structure into an amorphous form.

In the preparation of the additive, it may be coated for 70 to 280 seconds by applying a current of 20 to 60mA.

After the step of preparing the additive, performing the at least one of plasma etching and sputtering to process the surface of the coating layer; may further include.

In the stirring step, it can be stirred for 20 to 50 minutes using a propeller rotating at 100 to 500rpm.

After the stirring, passing the stirred additive and the solder through the through-hole to process into a solder ball; may further include.

Lead-free solder alloy composition manufacturing method according to an embodiment of the present invention comprises the steps of preparing an additive by forming a coating layer of a metal material on the surface of the carbon structure; Preparing a solder containing Sn in powder form; And mixing the additive and the solder in powder form with a flux to produce a solder paste, wherein the metal includes at least one of Ag, Ni, Pt, and Pd.

Bonding method between the member using the lead-free solder alloy composition according to an embodiment of the present invention comprises the steps of forming a first metal layer containing Cu on the surface of the first member of the material containing Al; Machining the surface of the first metal layer; And attaching a lead-free solder alloy composition to the first metal layer to bond the first member and a second member of a material including Al.

The lead-free solder alloy composition, the solder containing Sn; And an additive added to the solder, wherein the additive comprises: a carbon structure; And a coating layer of a metal material positioned on the surface of the carbon structure, wherein the metal may include one or more of Ag, Ni, Pt, and Pd.

After forming the first metal layer, forming a second metal layer including Cu on the surface of the second member; And processing the surface of the second metal layer.

The bonding may include disposing the lead-free solder alloy composition on the first metal layer; Positioning the second member such that the first metal layer and the second metal layer face each other with the lead-free solder alloy composition therebetween; And applying heat to the lead-free solder alloy composition.

The first member may be an Al frame having a step formed thereon, and the second member may be an Al material substrate. In the positioning, the second member may be seated on the step of the first member.

By using an additive made of a carbon structure coated with a metal material on the surface it can be expected to produce a lead-free solder alloy composition having excellent soldering properties, mechanical properties and thermal conductivity.

FIG. 1 is a view illustrating a carbon structure in which a metal coating layer is not formed, due to buoyancy in a molten solder.
2 is a view showing a state in which an additive made of a carbon structure in which a metal coating layer is formed in a molten solder according to an embodiment of the present invention.
3 is a photograph showing a state in which a carbon structure having a coating layer is uniformly dispersed in a solder base as an additive according to an embodiment of the present invention.
4 is a schematic diagram of a conventional Al mobile phone frame-bonded Al substrate using mechanical crimping, and an Al mobile phone frame-Al substrate is bonded using a lead-free solder alloy composition to which a carbon structure is added according to an embodiment of the present invention. to be.
Figure 5 is a schematic diagram showing the vessel used in the step of preparing the additive according to an embodiment of the present invention.
Figure 6 is a schematic diagram showing a propeller made of stainless steel used in the processing step according to an embodiment of the present invention.
7 is a graph showing the stirring conditions according to the stirring time and propeller rotation speed of the melt for the lead-free solder alloy composition in the stirring step according to an embodiment of the present invention.
Figure 8 is a field emission scanning electron microscope (FE-SEM) photograph showing the average grain size of the Examples and Comparative Examples according to the present invention.
9 is a graph measuring the tensile strength and elongation of the Examples and Comparative Examples according to the present invention.
10 is a graph measuring the wetting time of the Examples and Comparative Examples according to the present invention.
11 is a graph measuring the thermal conductivity of the Examples and Comparative Examples according to the present invention.
12 is a view showing a solderless solder alloy composition according to an embodiment of the present invention soldered onto an aluminum substrate on which a Cu metal layer having a surface uneven structure is formed by plasma etching.
FIG. 13 is an optical photomicrograph of a lead-free solder alloy composition soldered onto an aluminum substrate on which a Cu metal layer is formed according to an embodiment of the present invention. FIG.

Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, the first portion, component, region, layer or section described below may be referred to as the second portion, component, region, layer or section without departing from the scope of the invention.

The terminology used herein is for reference only to specific embodiments and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” include plural forms as well, unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” embodies a particular characteristic, region, integer, step, operation, element and / or component, and the presence of another characteristic, region, integer, step, operation, element and / or component or It does not exclude the addition.

When a portion is referred to as being "on" or "on" another portion, it may be directly on or on the other portion or may be accompanied by another portion in between. In contrast, when a part is mentioned as "directly above" another part, no other part is intervened in between.

Unless defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly defined terms used are additionally interpreted to have a meaning consistent with the related technical literature and the presently disclosed contents, and are not interpreted in an ideal or very formal sense unless defined.

In addition, unless otherwise indicated,% means weight% and 1 ppm is 0.0001 weight%.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Lead-free solder  Alloy composition

The lead-free solder alloy composition according to an embodiment of the present invention includes a solder and an additive.

The solder is formed of a material containing Sn. Specifically, in addition to Sn, Ag, Cu, Zn, Ni and Sb may further include one or more selected from.

More specifically, the solder may include, by weight, at least one of Zn and Sb: 0.5 to 95%, remainder: Sn, and unavoidable impurities.

Alternatively, the solder may include, by weight, at least one of Ag, Cu, and Ni: 0.5 to 20%, remainder: Sn, and unavoidable impurities.

The additive includes a carbon structure and a coating layer of metal material located on the surface of the carbon structure. The metal constituting the coating layer includes at least one of Ag, Ni, Pt, and Pd.

The presence of nano-controlled additives can improve the strength of the alloy by uniformly minimizing the matrix structure of the solder and the intermetallic compound (IMC) present in the solder. In addition, it is possible to prevent cracking of the solder and to suppress the formation of cavities. Accordingly, it is possible to prevent damage to the soldering portion joined to the electronic device, and to increase the reliability and life of the soldering portion.

As can be seen in FIG. 1, when the carbon structure is added to the solder as it is, the surface of the carbon structure is not wetted to the solder, and thus the carbon structure is pushed upward by the buoyancy of the solder.

On the other hand, as can be seen in Figure 2, when the metal coating layer is formed on the surface of the carbon structure, the solder is wet on the surface of the coating layer. Accordingly, the additive is attracted to the inside of the solder by the surface tension of the solder, and diffusion of the additive into the solder may occur. Therefore, the spreadability and wettability of the lead-free solder alloy composition may be improved.

The excellent solderability of lead-free solder alloy compositions is a great advantage for solder assembly of electronic circuits and electrical systems. These advantages can be applied to the sensitive electronic components or the circuit board during soldering, so that the soldering portion is firmly and stably formed, thereby reducing the soldering defect and improving the strength.

When the metal structure coated on the surface is used as an additive, when the solder is melted and solidified, the carbon structure having a much higher melting point than Sn (231 ° C.) is present as a fine nano-sized solid. These nano-sized solids can act as solid nucleation sites (seeds) upon solidification.

As a result, the added carbon structure provides a greater number of nucleation sites to allow solid crystals to be produced therein, so that the grains can be refined as compared with the case where the additive using the carbon structure is not added.

In addition, the carbon structure inhibits the growth of intermetallic compounds such as Ag ₃ Sn, Cu ₆ Sn _5, etc. in the solder that can be produced when the solder contains Sn and Ag or Sn and Cu, thereby miniaturizing the intermetallic compound. You can do that.

Accordingly, the soldering part contributes to further improved strength and characteristics by the Hall-Petch equation as follows.

In the case of a metal coating layer positioned on at least part of the surface of the carbon structure, the metal layer is formed of a metal material, and the metal includes at least one of Ag, Ni, Pt, and Pd.

Ag, Ni, Pt, and Pd may all form a coating layer on the surface of the carbon structure to improve bonding with the solder.

Specifically, when Ag is used as the material constituting the coating layer, it is possible to greatly improve the wettability between the carbon structure and the solder to expect a uniform dispersion effect in the solder of the carbon structure. In addition, when Ag is coated, it is possible to prepare a lead-free solder composition having excellent thermal and electrical conductivity.

On the other hand, the coating layer may have an average thickness of 20 to 500 kPa. When the average thickness from the surface of the carbon structure to the surface of the coating layer is less than 20 mm 3, the wettability improvement and the prevention of aggregation of the surface of the carbon structure may be insignificant. On the other hand, when it exceeds 500 kPa, excessive intermetallic compounds may be formed depending on the metal forming the coating layer, and problems of process cost and process time may occur.

Specifically, a convex-concave structure in which convex portions and concave portions are irregularly repeated on the surface of the coating layer may be formed.

Due to the presence of irregularities in which convex and concave portions formed on the surface of the coating layer are irregularly repeated, solder may be incorporated into the concave portion or the hollow hole of the surface of the coating layer according to the anchor effect. As a result, the mechanical bonding force may be increased to improve the strength of the soldered portion.

The additive may be included more than 0.01% and less than 5.0% based on 100% of the total weight of the lead-free solder alloy composition.

When the additive is included in 0.01% or less, the miniaturization effect by the additive is not so great that the improvement of solderability may be hardly seen. On the other hand, if it is included in the 5.0% or more, the solder is brittle, so that the cracks on the joint surface with the electronic device in the soldering portion may deteriorate solderability. This may cause dewetting, which is a poor wetting.

Specifically, the additive may have an average particle diameter of 1 nm to 100 μm.

When the average particle diameter of the additive is less than 1 nm, oxidation of the additive may easily occur, and handling may become difficult, thereby making it very difficult to expect a uniform dispersion effect. On the other hand, when the thickness exceeds 100 μm, the additives may coagulate with each other to deteriorate the solder characteristics.

Specifically, as shown in FIG. 3, the additive may be present in a dispersed form in the solder matrix. As mentioned above, as the metal coating layer is formed on the surface of the carbon structure, the solder may be wetted on the surface of the additive and diffusion of the additive into the solder may occur.

The carbon structure may include one or more materials of the carbon element allotrope.

For example, it may be graphene (graphene), graphite (graphite), carbon nanotubes (CNT), fullerene (fullerene) and the like.

When the carbon structure is graphene, the thickness may be 1 to 15 nm and a plate shape having a diameter of 25 μm or less. When the carbon structure is graphite, it may have an average particle diameter of 1 to 250nm in the form of a plate. When the carbon structure is carbon nanotubes, the diameter is 1 to 20nm, it may be in the form of 10㎛ or less in length.

The lead-free solder alloy composition according to one embodiment of the present invention can be used as a solder material. Specifically, it may be used for soldering pastes, solder balls, solder bars, solder wires, and the like, and electronic products using the same.

Specifically, as shown in Figure 4, it can be used for bonding between the Al mobile phone frame and the Al substrate that requires high thermoelectricity.

Modern electronic devices are becoming smaller and smaller to meet the needs of high integration, low power or portability, size, operating voltage and so on. One serious issue here is the wettability and strength of the soldering parts of electronic devices. In order to improve this, there is an increasing demand for a solder composed of an improved wettability and a finer Ag ₃ Sn compound, and the lead-free solder alloy composition according to an embodiment of the present invention can be effectively used to remedy this disadvantage.

Lead-free solder  Alloy composition manufacturing method

The method of manufacturing a lead-free solder alloy composition according to an embodiment of the present invention includes the steps of preparing an additive by forming a coating layer of a metal material on a surface of a carbon structure, melting a solder including Sn, and adding the additive and the molten solder. After mixing, the method includes stirring, and the metal includes at least one of Ag, Ni, Pt, and Pd.

Prior to preparing the additive, the method may further include grinding the carbon structure to form an amorphous carbon structure.

After preparing the additive, the method may further include processing the surface of the coating layer by performing one or more of plasma etching and sputtering.

After the stirring, the method may further include a step of passing the stirred additive and the solder through the through hole to process the solder ball.

In the step of forming the amorphous carbon structure, the carbon structure is pulverized to produce an amorphous carbon structure. It is disposed in the vessel (vessel) and the horizontally and vertically rotatable vessel shown in Figure 5, it is possible to crush the carbon structure through the principle of revolution and rotation using a blade-type impeller (impeller).

Specifically, an amorphous carbon structure may be manufactured using a vessel rotating at 10 to 60 rpm and an impeller rotating at 3000 to 14000 rpm in the vessel.

When the rotation speed of the impeller is faster than the rotation speed of the vessel, it is possible to prevent the carbon structure from sticking to the inner wall of the vessel due to the centrifugal force so that the contact with the impeller is difficult to be achieved. Accordingly, the grinding efficiency can be increased.

As the speed of rotation of the vessel and the impeller satisfies the above range, the carbon structure can be efficiently pulverized as the energy efficiency is increased, and the amorphous carbon structure can be manufactured.

After fabrication of the amorphous carbon structure, one or more of plasma etching and sputtering may be performed to process the surface of the carbon structure.

In the preparation of the additive, the surface of the carbon structure is coated with a metal material. This is a step to improve the spreadability and wettability of the carbon structure. When the carbon structure without metal coating is mixed with the solder as it is, the carbon structure is pushed upward due to the buoyancy of the solder because it does not wet well to the solder.

On the other hand, when the surface of the carbon structure is coated with a metal material, the solder is wetted on the surface of the additive, and the diffusion of the additive into the inside of the solder may occur because the additive is attracted to the inside by the solder surface tension. This can improve mechanical bonding and mixing between the solder bases.

Specifically, the carbon structure surface may be coated by metal vapor deposition or electroless plating such as physical vapor deposition (PVD), chemical vapor deposition (CVD).

In addition, a sputter coater may be used, and may be coated for 70 to 280 seconds with a current of 20 to 60 mA. By satisfying the above conditions, it is possible to expect a coating layer deposition effect of a uniform metal on the surface of the carbon structure.

Before forming the metal coating layer on the surface of the carbon structure, the carbon structure may be pulverized to be processed so that the carbon structure becomes amorphous, or the carbon structure having the metal coating layer formed by grinding the amorphous carbon having the metal coating layer formed thereon. The structure can be prepared. It does not matter in that order.

In processing the surface of the coating layer, one or more of plasma etching and sputtering may be performed to process the surface of the coating layer.

As such, by performing one or more processes of plasma etching and sputtering on the surface of the coating layer, an uneven structure in which convex and concave portions are irregularly repeated on the surface of the coating layer may be formed. Due to the formation of the concave-convex structure, the solder may be incorporated into recesses or hollow holes on the surface of the coating layer according to the anchor effect. As a result, the mechanical bonding force may be increased to improve the strength of the soldered portion.

Specifically, CF ₄ + O ₂ gas may be used. Plasma etching may be performed for 30 to 150 minutes under a vacuum degree of 20 to 50 mTorr. It can be sputtered for 60 to 300 seconds at a current of 10 to 50 mA under a vacuum degree of 0.01 to 1 mbar.

In the step of melting the solder, the solder containing Sn alone or at least one element selected from Ag, Ag, Cu, Zn, Ni, and Sb may be melted by heating in an electric furnace. Specifically, it may be melted at a temperature of 200 to 800 ℃.

In the stirring step, the lead-free solder alloy solder composition may be prepared by mixing and stirring the additive and the molten solder.

Specifically, it can be stirred for 20 to 50 minutes using a propeller rotating at 100 to 500rpm shown in FIG. If the speed of the propeller is less than 100rpm, the stirring may be insufficient and the dispersing effect of the additive may not be large. If it exceeds 500 rpm, if the solder is splashed or stirred in the atmosphere, the oxidation of the solder may be intensified. Therefore, the rotation speed of the propeller is controlled in the above range.

Figure 7 shows the optimum stirring conditions according to the stirring time and propeller rotation speed of the melt for the lead-free solder alloy composition.

The propeller may be made of stainless steel, and in this case, the reactivity of the surface of the propeller and the solder may be low, thereby improving stirring efficiency. In addition, a four-blade propeller having a thickness thinner than the diameter value of the shaft may be used. Accordingly, the effect of preventing the aggregation phenomenon of the additive and uniformly dispersing the additive in the molten solder can be expected.

In the step of processing into a solder ball can be processed into a solder ball by passing the stirred additive and the solder through the through hole.

It is possible to prepare a solder ball form by passing the composition of the stirred and molten state through a through hole having a constant size, such as an orifice plate.

In the method of preparing a lead-free solder alloy composition according to an embodiment of the present invention, preparing an additive by forming a coating layer of a metal material on a surface of a carbon structure, preparing a solder including Sn in powder form, and adding an additive and powder Mixing the solder in form with the flux to form a solder paste, wherein the metal comprises at least one of Ag, Ni, Pt, and Pd.

The description of the step of preparing the additive is replaced with the description of the method for producing a lead-free solder alloy composition.

Subsequently, a solder containing Sn alone or at least one element selected from Ag, Cu, Zn, Ni, and Sb may be prepared in powder form, mixed with the additives prepared before, and mixed with flux. It is prepared in the form of solder paste.

Lead-free solder  Joining method between members using alloy composition

Bonding method between the member using the lead-free solder alloy composition according to an embodiment of the present invention comprises the steps of forming a first metal layer containing Cu on the surface of the first member of the material containing Al, processing the surface of the first metal layer And adding a lead-free solder alloy composition to the first metal layer to bond the first member and the second member of the material including Al.

After forming the first metal layer, the method may further include forming a second metal layer including Cu on the surface of the second member and processing the surface of the second metal layer.

The step of machining the surface of the first metal layer and the step of machining the surface of the second metal layer are not limited in order and may be performed sequentially or simultaneously.

The lead-free solder alloy composition includes a solder containing Sn and an additive added to the solder, the additive including a carbon structure and a coating layer of a metal material disposed on the surface of the carbon structure, wherein the metal is Ag, Ni, Pt, and Pd. It contains 1 or more types.

Description of the lead-free solder alloy composition will be replaced by the above description.

According to the bonding method between the members using the lead-free solder alloy composition according to an embodiment of the present invention, the mechanical bonding force is increased due to the presence of the first metal layer having the surface processed to form the uneven structure, thereby improving the strength of the alloy. In addition, a good bonding surface excellent in thermal conductivity and free from defects such as voids and cracks can be obtained.

The first member and the second member are formed of a material containing Al and are not limited in shape.

In the forming of the first metal layer, a first metal layer made of Cu may be formed on the surface of the first member by using cladding, sputtering, plating, PVD, and CVD. Specifically, it may be around the connecting portion formed by the connection with the second member of the surface of the first member.

Meanwhile, the average thickness of the first metal layer formed using cladding, sputtering, plating, PVD, CVD, or the like may be 1 μm or more and 3 mm or less.

Thereafter, at least one of plasma etching and sputtering may be performed on the surface of the first metal layer to form an uneven structure in which convex portions and concave portions are irregularly formed.

Similarly, in the forming of the second metal layer, the second metal layer of Cu may be formed on the surface of the second member by using cladding, sputtering, plating, PVD, and CVD. Specifically, it may be around the connecting portion formed by the connection with the first member of the surface of the second member.

Meanwhile, the average thickness of the first metal layer formed using cladding, sputtering, plating, PVD, CVD, or the like may be 1 μm or more and 3 mm or less.

Thereafter, at least one of plasma etching and sputtering may be performed on the surface of the second metal layer to form an uneven structure in which convex portions and concave portions are irregularly formed.

Specifically, the step of bonding includes disposing a lead-free solder alloy composition on the first metal layer, placing the second member so that the first metal layer and the second metal layer face each other with the lead-free solder alloy composition therebetween; And applying heat to the lead-free solder alloy composition.

The lead-free solder alloy composition disposed on the first metal layer may be disposed along the first metal layer in the form of solder paste. Alternatively, the solder wire may be disposed along the first metal layer.

Thereafter, the second member may be positioned on the lead-free solder alloy composition so that the first metal layer and the second metal layer face each other such that the first metal layer and the second metal layer are connected to each other through the lead-free solder alloy composition.

Next, the lead-free solder alloy composition may be heated to bond the first member and the second member by the lead-free solder alloy composition.

The temperature for bonding the first member and the second member by heating may be 170 to 500 ° C. If the temperature is less than 170 ° C, it may be too low because the melting of the lead-free solder alloy composition is not performed properly bonding. On the other hand, if the temperature exceeds 500 ℃ can cause thermal damage to the substrate and the device may cause a problem in reliability.

Since both of the first metal layer and the second metal layer have concavo-convex structures formed on the surface thereof, when joined by the lead-free solder alloy composition, the solder is mixed into recesses or hollow holes on the surface of the coating layer according to the anchor effect. As the bonding force is increased, the bonding strength between the members can be improved.

Specifically, the first member is a frame made of Al material, the step is formed, the second member is an Al material substrate, in the step of positioning, the second member may be seated on the step of the first member.

As a first member constituting the mobile phone, an Al frame may be formed in a frame shape with one side open. A step may be formed inside. Steps can be formed by post-processing such as cutting.

Similarly, an Al substrate as a second member constituting the mobile phone may be seated on a step and connected to the first member.

Therefore, the first metal layer may be formed on the step of the first member, and may be formed on the edge of the second metal layer seated on the step. The lead-free solder alloy composition may be disposed between the first metal layer and the second metal layer to bond the first member and the second member.

More specifically, when seating the second member on the first member, it is possible to prevent the movement of the second member in the manufacturing process using a separate support, such as the connection position does not change.

Hereinafter, specific examples of the present invention will be described. However, the following examples are only specific examples of the present invention, and the present invention is not limited to the following examples.

One. Lead-free solder  Microstructure Properties of Alloy Compositions

Example 1

The vessel was rotated at 30 rpm and the impeller was rotated at 4000 rpm for 10 minutes to prepare crushed amorphous graphene.

Subsequently, an additive was prepared by coating Ag on the graphene surface using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 160 seconds with a current of about 40 mA. The thickness of the coated metal is about 300 mm 3.

Next, the surface of the coating layer was subjected to plasma etching. 95% CF ₄ + 5% O ₂ gas was used for the plasma etching, and was etched for about 120 minutes at a vacuum of 30 mTorr.

Sn-3.0 wt% Ag-0.5 wt% Cu solder was melted for about 30 minutes in a 450 ° C. temperature electric furnace in an atmosphere and nitrogen atmosphere. Thereafter, an additive in which an Ag coating layer was formed on the graphene surface was added to the molten solder at 0.2% based on the total weight of the composition, and stirred at 400 rpm for 20 minutes using a rectangular four-blade stainless steel propeller.

Comparative Example 1

A lead-free solder alloy composition was prepared in the same manner as in Example 1, except that a coating layer was not formed on the graphene surface.

Comparative Example 2

Sn-3.0wt% Ag-0.5wt% Cu solder was used without the addition of additives.

[Evaluation of Microstructure of Lead-Free Solder Alloy Compositions]

Example 1, where the Ag-coated additive on the graphene surface is Sn-3.0wt% Ag-0.5wt% Cu solder added 0.2% by weight of the total composition, the additive having no coating layer formed on the graphene surface Comparing the crystal grains of Comparative Example 1 which is Sn-3.0wt% Ag-0.5wt% Cu solder and Comparative Example 2 which is Sn-3.0wt% Ag-0.5wt% Cu solder without additive, the average grain size of Comparative Example 2 was compared. has been measured to be about ² 537.84㎛ average crystal grains of the Comparative example 1 is about the average grain 276.18㎛ ^2, example 1 was found to be about 264.32㎛ ^2. 8 shows FE-SEM photographs of Example 1, Comparative Example 1, and Comparative Example 2. FIG.

2. Lead-free solder  Mechanical Properties of Alloy Compositions

Example 2

The vessel was rotated at 20 rpm and the impeller was rotated at 5000 rpm for 7 minutes to prepare pulverized amorphous graphene.

Subsequently, an additive was prepared by coating Ag on the graphene surface using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 120 seconds with a current of about 50 mA. The thickness of the coated metal is about 200 mm 3.

Next, the surface of the coating layer was subjected to plasma etching. 95% CF ₄ + 5% O ₂ gas was used for the plasma etching, and was etched for about 70 minutes at a vacuum of 40 mTorr.

Sn-3.0 wt% Ag-0.5 wt% Cu solder was melted for about 30 minutes in a 450 ° C. temperature electric furnace in an atmosphere and nitrogen atmosphere. Thereafter, an additive having an Ag coating layer formed on the surface of graphene was added to the molten solder at 0.2% by weight of the total composition, and stirred at 300 rpm for 30 minutes using a rectangular four-blade stainless steel propeller.

Comparative Example 3

A lead-free solder alloy composition was prepared in the same manner as in Example 2, except that an additive was not formed on the coating layer on the surface of the carbon structure.

[Comparative Example 4]

Sn-3.0wt% Ag-0.5wt% Cu solder was used without the addition of additives.

[Evaluation of Mechanical Properties of Pb-Free Solder Alloy Compositions]

Tensile tests were carried out for Example 2, Comparative Example 3 and Comparative Example 4.

When the Ag-coated graphene is added to the solder, the tensile strength and elongation of the graphene having no metal coating layer formed on the solder and when no additive is added to the solder are confirmed through the graph of FIG. 9. Can be.

The tensile strength of Example 2 was 58.32 MPa, the tensile strength of Comparative Example 3 was 55.51 MPa, and the tensile strength of Comparative Example 4 was 54.73 MPa.

As a result, the addition of an additive consisting of a carbon structure in which a metal coating layer is formed on the surface makes the particles of the SAC305 solder fine and increases the strength. Alloys with fine grains further interfere with dislocation transfer and thus increase the mechanical properties of the alloy.

The elongation of Example 2 was 14.27%, the elongation of Comparative Example 3 was 12.51%, and the elongation of Comparative Example 4 was 10.43%.

As a result, there is an effect of increasing the strength and elongation due to the addition of an additive made of a carbon structure in which a metal coating layer is formed on the surface, thereby improving the toughness of the alloy.

3. Lead-free solder  Of alloy composition Solderability

Example 3

The vessel was rotated at 40 rpm and the impeller was rotated at 4000 rpm for 10 minutes to prepare pulverized amorphous graphene.

Subsequently, an additive was prepared by coating Ag on the graphene surface using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 120 seconds with a current of about 50 mA. The thickness of the coated metal is about 200 mm 3.

Next, the surface of the coating layer was subjected to plasma etching. 95% CF ₄ + 5% O ₂ gas was used for the plasma etching, and was etched for about 40 minutes at a vacuum of 40 mTorr.

Sn-3.0 wt% Ag-0.5 wt% Cu solder was melted for about 30 minutes in a 450 ° C. temperature electric furnace in an atmosphere and nitrogen atmosphere. Thereafter, an additive having an Ag coating layer formed on the graphene surface was added to the molten solder at 0.2% by weight of the total composition, and stirred at 400 rpm for 15 minutes using a stainless steel propeller having a rectangular 4-blade shape.

[Comparative Example 5]

To prepare a lead-free solder alloy composition in the same manner as in Example 3, using an additive not formed in the coating layer on the surface of the carbon structure.

Comparative Example 6

Sn-3.0wt% Ag-0.5wt% Cu solder was used without the addition of additives.

[Evaluation of Solderability of Pb-Free Solder Alloy Composition]

Solderability evaluation items are the evaluation of the wettability test (standard KSC IEC60068).

In the case of the wettability test, the shorter the zero cross time indicates the better wettability.

Wetting balance tester (RESCA SAT 5000) was used to measure the wettability of the solder, copper specimens were coated with BGA type flux, and the speed of 2.5mm / s to 2mm depth for 5 seconds on each molten solder at 250 ℃. Soaked in.

Wetting tests were carried out for Example 3, Comparative Example 5 and Comparative Example 6. Wetting of Example 3, Comparative Example 5 and Comparative Example 6 can be confirmed through the graph of FIG.

The wet time of Example 3 was 0.85 seconds, the wet time of Comparative Example 5 was 0.92 seconds, and the wet time of Comparative Example 6 was 1.02 seconds.

Good wettability is a great advantage for solder assembly in electronic circuits and electrical systems. These advantages are well spread on the sensitive electronic components or circuit boards during soldering, so that the soldered parts are formed firmly and stably, which serves as an advantage of reducing defects and improving strength of the soldered parts.

4. Lead-free solder  Thermal Conductivity of Alloy Compositions

Example 4

The vessel was rotated at 40 rpm and the impeller was rotated at 6000 rpm for 10 minutes to prepare pulverized amorphous graphene.

Subsequently, an additive was prepared by coating Ag on the graphene surface using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 120 seconds with a current of about 50 mA. The thickness of the coated metal is about 200 mm 3.

Next, the surface of the coating layer was subjected to plasma etching. 95% CF ₄ + 5% O ₂ gas was used for plasma etching, and was etched for about 100 minutes at a vacuum degree of 30 mTorr.

Sn-3.0 wt% Ag-0.5 wt% Cu solder was melted for about 30 minutes in a 450 ° C. temperature electric furnace in an atmosphere and nitrogen atmosphere. Thereafter, an additive in which an Ag coating layer was formed on the graphene surface was added to the molten solder at 0.2% by weight of the total composition, and stirred at 300 rpm for 20 minutes using a rectangular four-blade stainless steel propeller.

Comparative Example 7

A lead-free solder alloy composition was prepared in the same manner as in Example 4, except that an additive was not formed on the coating layer on the surface of the carbon structure.

Comparative Example 8

Sn-3.0wt% Ag-0.5wt% Cu solder was used without the addition of additives.

[Evaluation of Thermal Conductivity of Pb-Free Solder Alloy Compositions]

The thermal conductivity test was done about Example 4, the comparative example 7, and the comparative example 8. Thermal conductivity of Example 4, Comparative Example 7, and Comparative Example 8 can be confirmed through the graph of FIG.

The thermal conductivity of Example 4 was 44.271 / mK, the thermal conductivity of Comparative Example 7 was 43.864W / mK, and the thermal conductivity of Comparative Example 8 was 42.468W / mK.

As a result, it can be confirmed that the carbon structure in which the metal coating layer is formed on the surface has better thermal conductivity than the case in which the additive in which the metal coating layer is not formed is added and the additive is not added separately. This phenomenon may have a similar effect when not only the additives of the nanoparticles of the above embodiment, but also oxide, nitride, carbide, and boride nanoparticles of other elements.

5. Lead-free solder  With alloy composition cellphone  Frame splicing

Example 5

12 is a view showing a solderless lead-free solder alloy composition according to an embodiment of the present invention on a Cu coating layer having a surface uneven structure formed by plasma etching as a metal layer.

The vessel was rotated at 40 rpm and the impeller was rotated at 5000 rpm for 10 minutes to prepare pulverized amorphous graphene.

Subsequently, an additive was prepared by coating Ag on the graphene surface using a metal vapor deposition method. The equipment used for coating was a sputter coater and was coated for about 300 seconds with a current of about 50 mA. The thickness of the coated metal is about 400 mm 3.

Next, the graphene surface was subjected to plasma etching. 95% CF ₄ + 5% O ₂ gas was used for the plasma etching, and was etched for about 120 minutes at a vacuum of 30 mTorr.

Sn-3.0 wt% Ag-0.5 wt% Cu solder was melted for about 20 minutes in a 450 ° C. temperature electric furnace in an atmosphere and nitrogen atmosphere. Thereafter, an additive having an Ag coating layer formed on the surface of graphene was added to the molten solder at 0.2% based on the total weight of the composition, and stirred at 300 rpm for 30 minutes using a rectangular four-blade stainless steel propeller, thereby implementing the present invention. A lead-free solder alloy composition was prepared according to the example.

Example 6

A lead-free solder alloy composition was prepared in the same manner as in Example 5, except that an additive was not formed on the coating layer on the surface of the carbon structure.

Example 7

Sn-3.0wt% Ag-0.5wt% Cu solder was used without the addition of additives.

[Evaluation of Mobile Phone Frame Bonding Using Pb-Free Solder Alloy Composition]

Mobile phone frame bonding was implemented about Example 5, Example 6, and Example 7.

An aluminum 3003 substrate composed of 0.1% Cu-0.5% Fe-1.3% Mn-0.3% Si-0.1% Zn and the balance Al was prepared and processed to a 30 × 30 × 1 mm specification. After processing, the surface was polished and then washed, and a 100 μm metal layer of Cu was formed on the Al substrate surface. The equipment used was a sputter equipment, which was coated for 280 seconds with a current of 50 mA.

Plasma etching was applied to form irregularities on the surface of the metal layer.

The surface plasma etching step of the substrate has an effect of improving the strength of the alloy by increasing the mechanical bonding force as a result of the solder is mixed into the hollow hole or recess of the substrate by the anchor effect.

The lead-free solder alloy composition was placed on the prepared aluminum substrate on which the Cu metal layer was formed and joined by applying a temperature of 300 ° C.

13 is shown through an optical photomicrograph showing a state in which a lead-free solder alloy composition is soldered on an aluminum substrate on which a Cu metal layer is formed according to an embodiment of the present invention.

As a result of the joining, all of Example 5, Example 6, and Example 7 confirmed the favorable joining surface without defects, such as a void and a crack.

The present invention is not limited to the above embodiments and / or embodiments, but may be manufactured in various forms, and a person of ordinary skill in the art may change the technical spirit or essential features of the present invention. It will be appreciated that it can be practiced in other specific forms without doing so. Therefore, it should be understood that the embodiments and / or embodiments described above are exemplary in all respects and not restrictive.

Claims (19)

delete delete delete delete delete delete delete Pulverizing the carbon structure to form the carbon structure atypically;
Preparing an additive by forming a metal coating layer on a surface of the carbon structure;
Processing the surface of the coating layer by performing plasma etching;
Melting a solder containing Sn; And
And mixing the additives and the molten solder, followed by stirring.
The metal comprises at least one of Ag, Ni, Pt and Pd,
The additive has an average particle diameter of 1 nm to 100 µm,
Forming the carbon structure into an amorphous form using a vessel rotating at 10 to 60 rpm and an impeller rotating at 3000 to 14000 rpm in the vessel,
The plasma etching is plasma-etched for 30 to 150 minutes under CF ₄ and O ₂ gas atmosphere and 20 to 50mTorr vacuum degree,
Method for producing a lead-free solder alloy composition for stirring for 20 to 50 minutes using a propeller rotating at 100 to 500rpm in the stirring step. delete The method of claim 8,
In the step of preparing the additive,
Method for producing a lead-free solder alloy composition for coating for 70 to 280 seconds by applying a current of 20 to 60mA using a sputter coater. delete delete The method of claim 8,
After the stirring step,
Leading the stirred additive and the solder through the through-hole to process into a solder ball; further comprising a lead-free solder alloy composition manufacturing method. delete delete delete delete delete delete

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