KR20160139585A - Solder alloy, solder ball and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a silver halide photographic light-sensitive material comprising 1.5 to 2.5% by weight of silver (Ag); 0.5 to 1.5% by weight of copper (Cu); 0.03 to 0.08% by weight of nickel (Ni); 0.01 to 0.07% by weight of palladium (Pd); The remainder tin (Sn); And any inevitable impurities, and more particularly, to a solder alloy and a solder ball,
A solder alloy and a solder ball which are excellent in drop strength, thermal cycling (TC) characteristics, wetting ability and low missing rate when used in a printed circuit board, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solder alloy, a solder ball,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder alloy, a solder ball, and a method for manufacturing the same, more particularly, to a solder alloy used for a printed circuit board, A solder alloy having excellent solderability and a low missing rate, and a manufacturing method thereof.

Recently, portable digital devices with small and thin designs have become popular, while semiconductor packages mounted inside are becoming smaller and thinner. The semiconductor package is for electrically connecting, sealing, and packaging the semiconductor chips formed on the wafer so that the semiconductor chips can be used in real life. As portable digital devices become more sophisticated and multifunctional, the number of embedded semiconductor chips increases, while the size of the entire device is becoming smaller.

Therefore, reliability standards of solder joints applied to such electronic parts and portable digital devices have become very high and diversified. Particularly, the demand for a product that satisfies the thermal shock performance and the acceleration shock performance of the solder joint at the same time is rapidly increasing.

Particularly in portable products, there is a demand for miniaturization of a fine pitch of a printed circuit board (PCB) and a solder ball. As a result, the thickness of the PCB becomes thin, and warpage . Therefore, during the reflow process, which is a process of attaching the solder ball on the printed circuit board, a phenomenon in which the solder ball does not stick on the PCB, a large amount of missing is generated, and workability is greatly reduced. Therefore, as the solder ball becomes smaller, it is necessary to improve the reliability of the machining rate (the machining rate) which is increased more and more to the fine pitch.

In general, Sn-Ag-Cu alloys are used for reflow solder. Sn-Ag-Cu alloys have problems of oxidation and have problems such as wettability, heat resistance, durability strength needs to be improved.

Disclosure of the Invention The present invention has been conceived to solve the above-mentioned problems, and provides a composition of a solder alloy and a solder ball which simultaneously satisfies Drop strength strength and Thermal cycling (TC) characteristics and improves sewing rate and workability have.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a silver halide photographic light-sensitive material comprising 1.5 to 2.5% by weight of silver (Ag); 0.5 to 1.5% by weight of copper (Cu); 0.03 to 0.08% by weight of nickel (Ni); 0.01 to 0.07% by weight of palladium (Pd); The remainder tin (Sn); And any inevitable impurities.

The present invention also provides a solder alloy comprising at least one element selected from the group consisting of cobalt (Co), ruthenium (Ru), rhodium (Rh), lanthanum (La), cerium (Ce) and germanium do.

The present invention also provides a solder alloy wherein the content of the one element is 0.001 to 0.1 wt%, respectively.

The present invention also provides a solder alloy wherein the tin (Sn) is tin filtered through a vacuum refining or filter.

The present invention also relates to a silver halide photographic light-sensitive material comprising silver (Ag) in an amount of 1.8 to 2.2% by weight; 0.8 to 1.2% by weight of copper (Cu); The nickel (Ni) is 0.04 to 0.06 wt%; And 0.02 to 0.05% by weight of the palladium (Pd).

The present invention also relates to a method for producing a copper alloy comprising 1.5 to 2.5% by weight of silver, 0.5 to 1.5% by weight of copper, 0.03 to 0.08% by weight of nickel, 0.01 to 0.07% by weight of palladium, A method for producing a solder alloy in which tin (Sn) is introduced into a high-frequency vacuum induction furnace and made into an alloy according to a temperature rise profile under an inert atmosphere.

In another aspect, the present invention is a method for manufacturing a solder alloy of maintaining an inert atmosphere purged with and kept the inert atmosphere is a vacuum of a pressure of 3.0 × 10 ^-2 to 6.0 × 10 ^-2 torr, 750 to about 760 torr of an inert gas to provide.

Also, the present invention is characterized in that the heating profile includes a holding step after the first heating step and a holding step after the second heating step, wherein the first heating step temperature is 600 to 800 ° C and the second heating temperature is 1000 to 1200 ° C. A method for producing an alloy is provided.

In the present invention, tin (Sn) is a tin filtered impurities by vacuum refining, and a tin of 99.9% to 99.99% purity is injected into a vacuum furnace to remove impurities having higher vapor pressure and lower boiling point than tin Wherein the solder alloy is a tin alloy.

Further, according to the present invention, the tin (Sn) is tin filtered through a filter, and the molten tin having a purity of 99.9% to 99.99% is filtered through a filter made of ferritic stainless steel or austenitic stainless steel, At a pressure of 3 to 4 bar to remove impurities.

The present invention also relates to a silver halide photographic light-sensitive material, comprising 1.5 to 2.5% by weight of silver (Ag); 0.5 to 1.5% by weight of copper (Cu); 0.03 to 0.08% by weight of nickel (Ni); 0.01 to 0.07% by weight of palladium (Pd); And tin (Sn) containing any inevitable impurities of the remainder.

The solder ball is reflowed to a printed circuit board electroplated with nickel (Ni) / gold (Au), and the solder ball is plated on the printed circuit board electroplated with nickel / gold (Au) , Ni) ₆ Sn ₅ is formed on the first intermetallic compound layer and formation of a second intermetallic compound layer containing (Ni, Cu) ₃ Sn ₄ is suppressed on the first intermetallic compound layer, Thereby providing an increased solder ball.

The solder ball may be formed on a printed circuit board which is electroless plated with nickel (Ni) / gold (Au) when the solder ball is reflowed to a printed circuit board which is electroless plated with nickel (Ni) The formation of a dark layer including Ni ₃ P is suppressed to provide a solder ball with increased drop impact strength.

The present invention also relates to a method for the preparation of a silver halide emulsion comprising from 1.5 to 2.5% by weight of silver, from 0.5 to 1.5% by weight of copper, from 0.03 to 0.08% by weight of nickel, from 0.01 to 0.07% by weight of palladium, A solder alloy including tin (Sn) and any unavoidable impurities is melted in a molten metal, a master alloy is charged and held, and the solder alloy is heated by induction heating and passed through an orifice hole to form a solder ball And a manufacturing method thereof.

The present invention also provides a solder ball manufacturing method wherein the melting temperature is 230 to 250 ° C.

Also, the present invention provides a solder ball manufacturing method wherein the master alloy is a Sn-Ge master alloy and the holding temperature is 250 to 280 ° C.

The present invention also provides a method of manufacturing a solder ball in which the size of a ball manufactured by adjusting the frequency and the pressure is adjustable.

The present invention provides a composition of a solder alloy and a solder ball. When the solder ball according to the present invention is used for a printed circuit board, it has excellent drop strength, thermal cycling (TC) characteristics and wettability And the workability is improved because of a low missing rate.

More specifically, the present invention is characterized in that the wettability is enhanced by increasing the content of silver (Ag) as compared with the conventional ternary system alloy SAC105 (Sn1.0Ag0.5Cu), and the content of copper (Cu) It was reinforced. Compared with SAC305 (Sn3.0Ag0.5Cu), the content of silver (Ag) can be lowered and the thermal cycle characteristics may be degraded. However, by complementing the thermal cycle characteristics including nickel (Ni) and palladium (Pd) Characteristics and heat cycle characteristics at the same time.

1 is a graph showing the modulus according to the copper content.
Fig. 2 schematically shows the crack propagation behavior according to the modulus difference of the IMC.
3 is a photograph showing formation of a second intermetallic compound layer of SAC105, SAC305 and a solder ball according to an embodiment of the present invention.
4 schematically shows propagation behavior of cracks generated in the boundary region between the first intermetallic compound layer and the second intermetallic compound layer.
FIG. 5 is a photograph showing dark layer formation when the content of copper (Cu) is 0% by weight, 0.5% by weight and 1.0% by weight, according to an embodiment of the present invention.
Fig. 6 schematically shows the propagation behavior of cracks.
FIG. 7 is a photograph comparing the size of the intermetallic compound layer and the particle size according to the nickel (Ni) content.
8 is a schematic and SEM photograph of a conventional SAC solder to which palladium is not added and a Sn2.0Ag1.0Cu0.05Ni0.03Pd solder according to an embodiment of the present invention.
FIG. 9 shows a temperature condition cycle graph for measuring the thermal cycle characteristics.
FIG. 10 shows shear strength test results of solder balls according to an embodiment of the present invention.
FIG. 11 shows a comparison result of the failure mode of the solder ball after heat treatment according to an embodiment of the present invention.
FIG. 12 shows photographs showing the results of a missing test of the embodiment of the present invention and the comparative example.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

The solder alloy and the solder ball according to an embodiment of the present invention include silver (Ag), copper (Cu), nickel (Ni), palladium (Pd) and the remainder tin and any unavoidable impurities. More specifically, 1.5 to 2.5% by weight of silver (Ag); 0.5 to 1.5% by weight of copper (Cu); 0.03 to 0.08% by weight of nickel (Ni); 0.01 to 0.07% by weight of palladium (Pd); The remainder tin (Sn); And a solder alloy comprising any unavoidable impurities. When a solder ball manufactured using the solder ball is used for a printed circuit board, the strength of the drop strength, the thermal cycling (TC) characteristic, and the wettability (Wet- ability can be improved and the missing rate can be lowered.

The solder alloy and the solder ball according to the embodiment of the present invention have the physical properties similar to lead because the use of lead (Pb) is prohibited due to the regulation due to environmental pollution, and have good merits such as malleability, ductility, Based Sn solder alloy and a solder ball based on tin (Sn) having a Sn-based solder alloy.

However, in order to satisfy the characteristics required for solder balls such as drop strength, thermal cycling (TC) characteristics, and wettability, it is preferable to use an alloy with other metals rather than forming solder balls only with tin . The technical idea of the present invention is to provide a solder ball as a final product by using a solder alloy made by alloying silver (Ag), copper (Cu), nickel (Ni) and palladium (Pd) will be.

The solder alloy and the solder ball according to an embodiment of the present invention include silver (Ag). Ag has no self-toxicity. It lowers the melting point of the alloy, improves the spreadability of the base material, lowers the electrical resistance of the solder ball, improves thermal cycling (TC) characteristics and corrosion resistance.

When the content of silver in the solder alloy and the solder ball is 1.5 to 2.5 wt% and the content of silver is less than 1.5 wt%, it is difficult to sufficiently secure the electric conductivity and the thermal conductivity of the solder ball and the wet- And if it exceeds 2.5 wt%, a Bulky IMC called Ag ₃ Sn is formed inside the solder alloy and the solder ball, and the impact resistance of the solder is deteriorated due to overgrowth of the Bulky IMC. Preferably 1.8 to 2.2% by weight, more preferably 2.0% by weight.

The solder alloy and the solder ball according to an embodiment of the present invention include copper (Cu). Copper (Cu) can affect the bonding strength or the tensile strength, thereby improving dropping characteristics.

If the content of copper (Cu) in the solder alloy and the solder ball is 0.5 to 1.5 wt% and the content of copper (Cu) is less than 0.5 wt%, it is difficult to improve the bonding strength or tensile strength of the solder ball as much as desired, The solder is hardened and the breakage of the structure can easily occur, and the workability can be reduced. It is preferably 0.8 to 1.2% by weight, more preferably 1.0% by weight.

In order to strengthen drop impact strength, copper (Cu) content was increased compared to solder balls such as SAC305 and SAC105. In addition, when bonded to an OSP treated pad, increased copper (Cu) The modulus of the intermediate compound layer (IMC) is increased, and the intermetallic compound layer has a stiffness. Also, it has an effect of increasing the drop impact strength by lengthening the crack path by changing the broken crack mode to bulk.

FIG. 1 is a graph showing the modulus according to the content of copper, and FIG. 2 schematically shows the crack propagation behavior according to the modulus difference of IMC. When the modulus is small, the failure mode of Case 1 is observed more frequently, and when the modulus is large, the failure modes of Case 2 and Case 3 are observed.

In addition, the containing NiAu during electrolysis joined to the pad (pad) plated, (Cu, Ni) ₆ Sn to form a first intermetallic compound layer containing _5, reflow after step (Ni, Cu) ₃ Sn ₄ 2 intermetallic compound layer is formed. When a second intermetallic compound layer is formed, a lattice mismatch with the first intermetallic compound layer is generated. When a drop impact occurs, cracks are generated in the boundary between the first intermetallic compound layer and the second intermetallic compound layer Lt; / RTI > As in the embodiment of the present invention, when the content of copper (Cu) is high, the formation of the second intermetallic compound layer is suppressed, and this behavior has the effect of increasing drop impact strength.

FIG. 3 is a photograph of SAC105, SAC305, and a second intermetallic compound layer of the solder ball according to the present invention. FIG. 4 is a graph showing the crack propagation behavior generated in the boundary region between the first intermetallic compound layer and the second intermetallic compound Respectively.

When bonding to a NiAu electroless plated pad, a dark layer containing Ni ₃ P is formed between the bonding layer and the pad after the reflow process. The dark layer has a weak characteristic. The present invention can control the thickness of the dark layer which adversely affects the reliability by increasing the copper (Cu) content, and this behavior has the effect of improving drop impact strength.

FIG. 5 shows a dark layer formation image when the content of copper (Cu) is 0% by weight, 0.5% by weight and 1.0% by weight, and the propagation behavior of cracks is schematically shown in FIG.

The solder alloy and the solder ball according to an embodiment of the present invention include nickel (Ni). Nickel (Ni) improves the flow characteristics at the time of melting and improves thermal cycle characteristics and drop impact characteristics.

The content of nickel (Ni) in the solder alloy and the solder ball is 0.03 to 0.08% by weight. When the content of nickel (Ni) is less than 0.03% by weight, the effect is insignificant. There is a problem that the flowability is lowered at the time of melting. Preferably 0.04 to 0.06% by weight, and more preferably 0.05% by weight.

Nickel (Ni) plays a role of making the internal structure of the bulk finer and eliminating the compressive stress generated in the intermetallic compound layer, so that the drop impact strength is increased by this behavior. FIG. 7 shows photographs for comparing the formation of the intermetallic compound layer and the particle size according to the nickel (Ni) content.

The solder alloy and the solder ball according to an embodiment of the present invention include palladium (Pd). Palladium (Pd) improves thermal cycling and drop impact properties.

The content of palladium (Pd) in the solder alloy and the solder ball is 0.01 to 0.07% by weight. When the content of palladium (Pd) is less than 0.01% by weight, the effect is insignificant. When the content of palladium (Pd) ripening. Preferably 0.02 to 0.05% by weight, and more preferably 0.03% by weight.

The solder alloy and the solder ball according to an embodiment of the present invention include palladium (Pd), thereby making the structure of the solder finer, forming a rough intermetallic compound layer containing PdSn ₄ in the structure (bulky IMC) Cracks along the cycle proceed along the grain boundary, and propagating cracks have the effect of improving the thermal cycle characteristics by meeting fine particles and coarse intermetallic compounds.

8 is a schematic and SEM photograph of a conventional SAC solder without palladium and a Sn2.0Ag1.0Cu0.05Ni0.03Pd solder according to an embodiment of the present invention.

Most of the solder alloys used in the past are mainly ternary alloys having tin (Sn), silver (Ag) and copper (Cu) as the basic composition. As the content of silver (Ag) , While the temp cycle performance tends to improve. In contrast, as the content of silver (Ag) decreases, the drop impact strength tends to improve but the thermal cycle characteristic tends to decrease.

On the other hand, the present invention has enhanced the wettability by increasing the content of silver (Ag) as compared with the conventional ternary alloy SAC105 (Sn1.0Ag0.5Cu), and the drop impact strength is enhanced by increasing the content of copper (Cu). Compared with SAC305 (Sn3.0Ag0.5Cu), the content of silver (Ag) can be lowered and the thermal cycle characteristics may be degraded. However, by complementing the thermal cycle characteristics including nickel (Ni) and palladium (Pd) Characteristics and thermal cycle characteristics of the solder alloy and the solder ball of the present invention.

The solder alloy and the solder ball according to an exemplary embodiment of the present invention may include at least one selected from the group consisting of cobalt (Co), ruthenium (Ru), rhodium (Rh), lanthanum (La), cerium (Ce), and germanium Element. At least one element selected from the group consisting of cobalt (Co), ruthenium (Ru), rhodium (Rh), lanthanum (La), cerium (Ce) and germanium (Ge) Because of the high reactivity and high oxygen consumption during the reaction, the amount of oxide in the alloy is reduced through sacrificial oxidation to lower the segregation rate.

The one or more elements may be contained in an amount of 0.001 to 0.1% by weight, respectively. Particularly, when the content of lanthanum (La), cerium (Ce) and germanium (Ge) exceeds 0.1% by weight, the tendency to react with external oxygen and form oxides is greater than the effect of reducing oxides in alloys , But rather increases the segregation rate of the alloy.

When the two or more elements are included, the sum of the contents of the elements is preferably 0.001 to 0.2% by weight.

Cobalt (Co) does not form a compound with silver (Ag) and copper (Cu), but forms a quadrivalent CoSn ₂ compound with tin (Sn). Ruthenium (Ru) and rhodium (Rh) form cubic Ru ₃ Sn ₇ and tetradentate RhSn ₂ compounds because it is more stable to form compounds with tin (Sn).

CoSn ₂ , Ru ₃ Sn ₇ and RhSn ₂ compounds are uniformly distributed throughout the solder and reduce interfacial energy inside the solder, thereby finely grain boundary. Further, since the grain boundary fineness tends to be larger than that of lanthanum (La) and cerium (Ce), it has better fall impact strength and heat cycle characteristics.

Lanthanum (La) and cerium (Ce) form cubic LaSn3 and CeSn3 compounds because it is more stable to form compounds with tin (Sn). These compounds are uniformly distributed throughout the solder, lowering the interfacial energy, increasing the mechanical strength due to grain boundary refinement, and simultaneously improving drop impact strength and thermal cycle characteristics.

Germanium (Ge) exists in the solder as a tetragonal structure on a gel with the same structural characteristics as the? -Sn phase, and is an amorphous phase formed during cooling of the solder alloy, the GeySn1-y compound, Y is a random real number value that can not be specified since it is a random structure with no regularity in the array). The structural properties of these compounds interfere with crack propagation caused by physical impact and thermal fatigue, improving the physical and thermal performance of the solder alloy.

The solder alloy and the solder ball according to an embodiment of the present invention may use processed tin (Sn) as the remaining tin (Sn). For example, tin filtered impurities may be used through vacuum refining or filtering.

The tin, which has a large amount of impurities releasing alpha radiation such as lead (Pb) and bismuth (Bi) through vacuum refining, can be used as a main source of alpha radiation from tin by using the difference in the vapor pressure of the tin and the impurities contained in the tin. (B), antimony (Sb), and arsenic (As) are removed through vacuum distillation to suppress the emission of alpha radiation as much as possible. Preferably, tin having lead (Pb) of 30 ppb or less and bismuth (Bi) of 250 ppb or less is used.

Tin filtered impurities through a filter is made by passing molten tin having a purity of 99.9% to 99.99% in a ferrite-based stainless steel or a filter having an austenitic stainless steel material with a hole of 2 to 7 탆 under a pressure of 3 to 4 bar to produce lead (Pb ), Iron (Fe), bismuth (Bi), aluminum (Al) and zinc (Zn) are removed and the concentration of each of the impurities is 10 ppm or less.

According to one embodiment of the present invention, when processed tin is used, the Mushy region is minimized as compared with the case where general tin is used. When the liquid phase changes to a solid phase, the liquid phase and the solid phase are simultaneously present. When the liquid phase changes into a solid phase, impurities such as Pb and Fe are present, and the respective elements exist as one phase. By creating sites and increasing the time to solidify, the machine area will increase. When the solder balls are bonded, a fast reaction must occur. In the case where the machice area is large, the reaction time is long and the bonding reaction is slowed, so that the machice area should be minimized.

Hereinafter, a method of manufacturing the solder alloy and the solder ball according to another aspect of the present invention will be described.

A method of manufacturing a solder alloy according to an embodiment of the present invention is a method of manufacturing a solder alloy including at least one of silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), and tin (Sn) in a high frequency vacuum electric induction furnace ), And the alloy is produced in an inert atmosphere according to the temperature rising profile.

More specifically, the silver (Ag), the silver (Ag), the copper (Cu) in an amount of 0.5 to 1.5 wt%, the nickel (Ni) in an amount of 0.03 to 0.08 wt%, the palladium (Pd) in an amount of 0.01 to 0.07 wt% Tin (Sn) is introduced into a high-frequency vacuum induction furnace and the above process is performed to produce a solder alloy having a composition according to the present invention.

Inert atmosphere, after keeping the degree of vacuum at a pressure of 3.0 × 10 ^-2 to 6.0 × 10 ^-2 torr, and purged with 750 to 760 torr of an inert gas to maintain an inert atmosphere.

When the degree of vacuum drops to 10 ^-1 torr, oxygen reacts with tin to form a large amount of tin oxide. In the case of producing an alloy in a high-frequency vacuum induction furnace, the unnecessary reaction of tin to form tin oxide (SnO ₂ ) by reaction with oxygen is suppressed, so that the content of other elements is less changed and the segregation rate is reduced.

Further, the agitating force due to the electrical vortex in the high-frequency vacuum induction furnace is superior to the mechanical agitating force of the conventional method using the electric furnace, and work is performed in an inert atmosphere rather than in the atmosphere.

The purging means that the inside of the alloy is neutralized with an inert gas which does not cause a chemical or physical reaction, and it is preferably maintained for 5 to 15 minutes after the purging.

The temperature rise profile includes a maintenance step after the first temperature rise and a maintenance step after the second temperature rise. The primary heating temperature is preferably 600 to 800 占 폚, and the secondary heating temperature is preferably 1000 to 1200 占 폚. It is preferable that the primary heating and the secondary heating are performed for 5 minutes to 15 minutes. Further, it is preferable to include a holding step after the first heating and after the second heating, respectively, and it is preferable to maintain the temperature for 5 to 15 minutes after the first heating and 50 to 70 minutes after the second heating.

That is, after purging, the solder alloy is manufactured through an elevated temperature profile in which the temperature is raised to 600 to 800 ° C for 5 to 15 minutes, and then the temperature is maintained for 5 to 15 minutes, and further, the temperature is raised to 1000 to 1200 ° C for 5 to 15 minutes and then maintained for 50 to 70 minutes . By maintaining the temperature for 50 to 70 minutes after the second heating, constituent elements having different specific gravities can be alloyed homogeneously.

Hereinafter, a tin processing method for providing a solder alloy and a solder ball manufactured using the processed tin according to an embodiment of the present invention will be described in detail.

A method for producing tin in which impurities releasing alpha radiation are largely removed using vacuum refining comprises first preparing a raw material tin having a purity of 99% to 99.99%. In the present specification, tin, which is a raw material of solder, is exemplified. However, the tin is used, for example, in a tin-based alloy containing 1.5 to 2.5% by weight of silver (Ag) or 0.5 to 1.5% by weight of copper .

Next, as the pretreatment step, the prepared tin is immersed and washed in a washing tank containing diluted hydrochloric acid solution (7 to 12%) for about 5 to 10 minutes. Then, the washed tin is immersed in a washing tank containing acetone (or ethanol) or distilled water, and then the washed tin is taken out and dried with nitrogen or air. Further, the crucible which is provided inside the vacuum furnace and receives tin is washed with hydrochloric acid for 50 to 60 minutes, and then dried with nitrogen gas. At this time, the crucible may be a container made of quartz or alumina plate. Among them, it is preferable to use a container made of high-purity quartz plate to prevent impurities from being mixed into tin.

Here, the vacuum furnace is generally known in the art as long as it can remove the impurities such as lead and bismuth which are the main sources of alpha radiation from tin by using the difference of the vapor pressure of each element, Or a vacuum furnace other than a box type or other type of vacuum furnace.

After the pretreatment process, tin is placed on a crucible and placed in a vacuum furnace. Subsequently, steam is supplied to the vacuum furnace at a predetermined temperature, pressure and time condition to remove impurities such as lead, bismuth, antimony, and arsenic, which have a higher vapor pressure and a lower boiling point than tin, from the tin. At this time, the predetermined temperature is 1000 ° C. to 1300 ° C., the pressure is 0.01 to 30 millitorr, the time is 2 to 6 hours, and the temperature for the vacuum furnace is 5 ° C. to 30 ° C. per minute Lt; 0 > C to 1300 < 0 > C.

That is, the method of filtering the tin using the vacuum refining according to the present invention utilizes the difference in the vapor pressure of the elements such as tin, lead, bismuth, and antimony at the same temperature. As a result, the high vapor pressure and the low boiling point lead, And antimony can be separated from the tin by distillation.

Specifically, tin has a low melting point and a high boiling point, and impurities such as lead, bismuth, and antimony contained in the tin have a boiling point lower than that of the tin and a high vapor pressure at the same temperature, It is possible to remove impurities having a boiling point.

Then, to remove the vacuum-refined tin, the vacuum is cooled at a rate of 5 [deg.] C to 30 [deg.] C per minute until the temperature reaches approximately 20 [deg.] C to 30 [deg.] C to cool the impurity-removed tin. Thereafter, the tin removed from the impurities is removed from the vacuum furnace, and then the tin is washed with nitrogen gas to remove carbon and other contaminant particles to complete the production of tin.

A method for producing tin filtered through a filter is to pass tin at a purity of 99.9% to 99.99% at 250-350 ° C and then under a pressure of 3 to 4 bar to a filter device having a filter of 2 to 7 μm pores.

Since the melting point of tin is 232 deg. C, the melting operation is not smooth at 250 deg. C or lower, and the filtering effect is insufficient because the tin is highly oxidized due to the high temperature at 350 deg. Preferably, the tin is melted at 290 to 310 占 폚.

The material of the filter is ferritic stainless steel or austenitic stainless steel. The stainless steel may further include at least one of molybdenum, nickel, and chromium. For example, when molybdenum is contained in an amount of 6% or less, it has an effect of being able to withstand cracks and stress, and when it contains 13% or more of chromium, it has an effect of giving high oxidation resistance. When the content of nickel is less than 10%, it has an effect of maintaining the austenite structure from the melting point to the low temperature.

The size of the filter hole is in the range of 2 to 7 μm, and when it is less than 2 μm, the workability is deteriorated.

Also, when the pressure is less than 3 bar and greater than 4 bar, there is no filtering effect.

After the tin filtering, the impurities such as Pb, Fe, Bi, Al, Zn are removed and the concentration of each impurity becomes 10 ppm or less. The filtered tin has lower concentration of oxygen than that of unfiltered tin and relatively high concentrations of Sn, Ag, Cu, etc., and minimizes the Mushy region.

A method of manufacturing a solder ball according to an embodiment of the present invention includes forming a solder alloy including silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), tin (Sn), and any inevitable impurities Is melted in a molten metal, and a master alloy is fed and held. Then, the mixture is induction-heated and passed through an orifice hole to produce a ball of a predetermined size.

More specifically, the present invention provides a method of manufacturing a semiconductor device comprising 1.5 to 2.5% by weight of silver, 0.5 to 1.5% by weight of copper, 0.03 to 0.08% of nickel, 0.01 to 0.07% The palladium (Pd) and the remainder of tin (Sn) is used for the above process to produce a solder ball having the composition according to the present invention.

The master alloys are made by melting an alloy containing a large amount of Sn (Sn-Ge master alloy) separately and adding it to the melt of the base metal (general tin or processed tin) In order to uniformly add a predetermined amount of an alloying element to be added when preparing a desired alloy. In addition, since the melting point (938 ° C) of Ge alone is high, a master alloy is prepared to lower the melting point. The master alloy includes tin (Sn) and germanium (Ge), and preferably includes 0.1 to 5 parts by weight of germanium relative to 100 parts by weight of tin, but is not limited thereto.

Induction heating is a method of converting electric energy into heat energy by electromagnetic induction and using it as a method of heating Joule's heat generated when a secondary current induced by electromagnetic induction flows into a material to be heated. In this case, the material to be heated is an alloy to which a master alloy is added.

The size of the solder balls formed can be controlled by frequency and pressure. The solder balls formed using the orifice holes having a diameter of 70 to 120 mu m, a frequency of 7 to 15 KHz, and a pressure of 1000 to 2000 mbar have an average diameter of 150 to 250 mu m. The orifice is made of graphite material and can be realized in a stable size and has a cylindrical shape.

The solder balls manufactured according to one embodiment of the present invention can be used in a semiconductor package. The solder ball according to the embodiment of the present invention is not limited to the use of the semiconductor package and can be used for various purposes. In particular, the semiconductor package according to various embodiments of the present invention may be applied to a package on package (PoP) in which a top package is stacked on a bottom package in a stacked manner in which a plurality of integrated circuits are mounted on a single substrate.

Examples and Comparative Examples

A solder ball was prepared with the same composition as shown in Table 1 below.

In Examples 1 to 7, silver, copper, nickel, and palladium were weighed using a 3N (99.9%) tin in a weight ratio of contents as shown in Table 1 below to prepare a solder alloy in a high frequency vacuum induction furnace, The solder alloy was melted in the molten metal and Sn-Ge master alloy was added. After induction heating for 5 minutes, solder balls with an average diameter of 250 μm were produced through the orifice holes.

In Examples 8 to 11, solder balls having compositions as shown in Table 1 below were prepared using tin filtered through vacuum refining. Examples 12 to 15 use tin filtered impurities through a filter Thereby preparing a solder ball having the composition shown in Table 1 below.

In Comparative Examples 1 to 5, 3N (99.9%) tin was used to produce a solder ball having the components and contents shown in Table 1 below.

Sn Ag
(wt%) Cu
(wt%) Ni
(wt%) Pd
(wt%) Sn machining whether Example 1 Remain 1.5 0.5 0.03 0.01 X Example 2 Remain 1.8 0.8 0.04 0.02 X Example 3 Remain 2.0 1.0 0.03 0.01 X Example 4 Remain 2.0 1.0 0.05 0.03 X Example 5 Remain 2.0 1.0 0.06 0.05 X Example 6 Remain 2.2 0.8 0.06 0.05 X Example 7 Remain 2.5 0.5 0.08 0.07 X Example 8 Remain 1.5 1.5 0.05 0.03 O Example 9 Remain 1.8 1.2 0.05 0.03 O Example 10 Remain 2.0 1.0 0.04 0.02 O Example 11 Remain 2.0 1.0 0.05 0.03 O Example 12 Remain 2.0 1.0 0.05 0.03 O Example 13 Remain 2.0 1.0 0.08 0.07 O Example 14 Remain 2.2 1.2 0.05 0.05 O Example 15 Remain 2.5 1.5 0.05 0.03 O Comparative Example 1 Remain 3.0 0.5 - - X Comparative Example 2 Remain 1.0 0.5 - - X Comparative Example 3 Remain 2.0 1.0 - - X Comparative Example 4 Remain 1.2 0.5 0.05 - X Comparative Example 5 Remain 1.0 0 0.05 - X

Experimental Example

Hereinafter, characteristics of the solder ball according to the composition range of the component of the solder ball according to an embodiment of the present invention will be examined based on experimental data. In order to investigate the characteristics of the solder balls, the drop impact strength, thermal cycle characteristics, wettability and miscutting rate of the specimens prepared by the following reflow process were tested.

≪ Reflow process >

Solder balls manufactured according to the embodiment and the comparative example of the present invention were mounted on a Ni / Au (Electrolytic) printed circuit board (PCB) using Attach equipment, and a reflow process was performed . The WS (Water Soluble) type was used for the flux. The peak temperature was 240 ㅁ 5 ℃, the dwell time was 40 ㅁ 10s (over 220 ℃), and the atmosphere was 3000 ppm O ₂ contents.

A reflow operation was performed under the same conditions as above to prepare a specimen in which the Ni / Au PCB bonded with the solder ball was bonded to an organic film coated (Organic Solderability Preservative, OSP) board. Respectively.

(1) Shearing strength test

The specimens were exposed to high temperature, high humidity and high temperature in order to measure the shear strength and fracture mode due to heat treatment. In the case of high temperature and high humidity, 96 hours and 168 hours were carried out at a temperature of 130 ° C-85%, and 250 hours and 500 hours at 150 ° C, respectively. The shear strength before heat treatment and the failure mode after heat treatment were compared.

As shown in FIG. 10, the shear strength value of the example is higher than the shear strength value of the comparative example, and the IMC failure mode after the heat treatment is small as shown in FIG. It can also be deduced that this results in excellent thermal cycle life characteristics as a result of the thermal cycle test described later.

IMC (Intermetallic compound) is an intermetallic compound formed by interactions such as electron movement occurring at the junction between the solder ball and the metalized layer (NiAu) of the PCB. As the IMC region becomes larger, the IMC breakage (IMC fracture.

The grain size of Ni and Pd added by the present invention is finer and the back diffusion of Au moving along the grain boundary is impeded and the relatively weak AuSn ₄ IMC It is possible to minimize the formation of the overcoat layer.

(2) Drop impact strength measurement

In order to test the drop impact strength of the specimen, it was carried out according to the JESD22-B111 specification. Specifically, the number of drops that caused the fracture was measured by applying an impact amount of 1500 G, 0.5 msec of gravity acceleration to the solder ball bonded PCB. The results are shown. The fracture of the specimen was recognized as failure when the initial resistance was increased by 10% or more, and the drop impact resistance value of 3 of 5 consecutive drop evaluations was recognized as failure when the initial resistance increased by 10% or more.

Drop 1% Destruction
(number of drops) Drop 10% Destruction
(number of drops) Example 1 96 142 Example 2 92 139 Example 3 113 172 Example 4 116 186 Example 5 114 169 Example 6 102 155 Example 7 108 164 Example 8 102 154 Example 9 96 142 Example 10 114 171 Example 11 136 214 Example 12 124 205 Example 13 118 179 Example 14 98 152 Example 15 82 132 Comparative Example 1 20 32 Comparative Example 2 45 72 Comparative Example 3 78 124 Comparative Example 4 84 128 Comparative Example 5 12 20

As shown in Table 2, the drop impact characteristics of the examples are superior to those of the comparative example. Particularly, when 2.0 wt% of Ag, 1.0 wt% of Cu, 0.05 wt% of Ni and 0.03 wt% of Pd were filtered It can be seen that the solder ball of Example 11 using tin remained has the best drop impact property.

(3) Evaluation of thermal cycle characteristics

In order to measure the thermal cycle characteristics of the specimen, the test was carried out under the condition of -40 ° C to 125 ° C according to the JEDS22-A104-B standard. As shown in FIG. 9, the number of cycles at which fracture occurred was measured by maintaining the temperature at 125 DEG C for 10 minutes and then changing the temperature to -40 DEG C for 10 minutes. As a result, the test results are shown in Table 4. The criterion for specimen destruction was measured every 100 cycles, and excluded from the specimen when shorted.

Thermal cycle 1% destruction
(number of cycles) Thermal cycle 10% destruction
(number of cycles) Example 1 1326 2142 Example 2 1204 1936 Example 3 1708 2802 Example 4 1826 2978 Example 5 1742 2797 Example 6 1468 2384 Example 7 1556 2520 Example 8 1032 1684 Example 9 984 1594 Example 10 1116 1802 Example 11 2124 3242 Example 12 1984 3082 Example 13 1106 1786 Example 14 1068 1729 Example 15 1002 1613 Comparative Example 1 1532 2498 Comparative Example 2 1036 1658 Comparative Example 3 1338 2161 Comparative Example 4 965 1554 Comparative Example 5 1126 1802

As shown in Table 3, the thermal cycle characteristics show that the TC lifetime increases with an increase in silver (Ag) content. Particularly, Ag 2.0 wt%, Cu 1.0 wt%, Ni 0.05 wt%, Pd 0.03 wt% It can be seen that the solder ball of Example 11 using remnant of tin filtered through vacuum refining has the best thermal cycle characteristics.

(4) Wet-ability evaluation

800 g of an alloy was melted in a molten metal at 240 ° C., and a flux was applied to a Cu plate and dropped on a bath. The results were shown in Table 4. The wettability is measured by the wetting time (T0). The shorter the wetting time, the better the wettability.

Wettability (T0) (sec.) Example 1 1.13 Example 2 1.18 Example 3 1.18 Example 4 1.12 Example 5 1.22 Example 6 1.14 Example 7 1.15 Example 8 0.56 Example 9 0.58 Example 10 0.52 Example 11 0.48 Example 12 0.78 Example 13 0.80 Example 14 0.81 Example 15 0.82 Comparative Example 1 1.51 Comparative Example 2 1.64 Comparative Example 3 1.42 Comparative Example 4 1.72 Comparative Example 5 1.83

As shown in Table 4, when the purified tin was used, 2.0 wt% of Ag, 1.0 wt% of Cu, 0.05 wt% of Ni, 0.03 wt% of Pd It can be seen that the solder ball of Example 11 using remnant of tin filtered through vacuum refining in wt% has the best wettability.

(5) Missing rate measurement

The specimens were heat-treated at 85 ° C-85% to evaluate the cutting rate. 100 strips, and the solder ball missing ratio can be calculated as follows.

Overall, the rate at which a missing bump occurred was calculated by dividing the number of missing bumps by the number of bumps present per unit multiplied by the number of units. The number of bumps present per unit is 778. In general, when the sewing rate is less than 600 ppm, the semiconductor package operation can be smoothly performed. Solder balls having an average diameter of 250 mu m were used.

Pkg. design Ball size Missing rate Pad finish SR Opening Example 1 NiAu 220um 250um 586 ppm Example 2 NiAu 220um 250um 602 ppm Example 3 NiAu 220um 250um 614 ppm Example 4 NiAu 220um 250um 563 ppm Example 5 NiAu 220um 250um 572 ppm Example 6 NiAu 220um 250um 605 ppm Example 7 NiAu 220um 250um 596 ppm Example 8 NiAu 220um 250um 64 ppm Example 9 NiAu 220um 250um 72 ppm Example 10 NiAu 220um 250um 58 ppm Example 11 NiAu 220um 250um 42 ppm Example 12 NiAu 220um 250um 224 ppm Example 13 NiAu 220um 250um 236 ppm Example 14 NiAu 220um 250um 244 ppm Example 15 NiAu 220um 250um 264 ppm Comparative Example 1 NiAu 220um 250um 8548 ppm Comparative Example 2 NiAu 220um 250um 9624 ppm Comparative Example 3 NiAu 220um 250um 6854 ppm Comparative Example 4 NiAu 220um 250um 16548 ppm Comparative Example 5 NiAu 220um 250um 18548 ppm

FIG. 12 is a photograph showing the results of the missing test of Examples 4 and 11 and Comparative Examples 1 and 4, and a portion where a relatively bright portion appears is a region where a missing portion is generated. The Sn1.2Ag0.5Cu0.05Ni solder of Comparative Example 4 showed the most missing and the Sn2.0Ag0.5Cu0.05Ni0.03Pd solder using the processed tin of Example 11 had the lowest missing You can see what you see.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

Claims (17)

1.5 to 2.5% by weight of silver (Ag);
0.5 to 1.5% by weight of copper (Cu);
0.03 to 0.08% by weight of nickel (Ni);
0.01 to 0.07% by weight of palladium (Pd);
The remainder tin (Sn); And
A solder alloy comprising any inevitable impurities. The method according to claim 1,
Wherein the solder alloy further comprises at least one element selected from the group consisting of Co, Ru, Rh, La, Ce and Ge. 3. The method of claim 2,
Wherein the content of the one kind of element is 0.001 to 0.1 wt%, respectively. The method according to claim 1,
Wherein the tin (Sn) is tin filtered impurities through a vacuum refining or filter. The method according to claim 1,
The silver (Ag) is 1.8 to 2.2 wt%;
0.8 to 1.2% by weight of copper (Cu);
The nickel (Ni) is 0.04 to 0.06 wt%;
And 0.02 to 0.05% by weight of palladium (Pd). (Ni), 0.01 to 0.07 wt% of palladium (Pd), and the remainder of tin (Sn) in an amount of 1.5 to 2.5 wt% of silver (Ag), 0.5 to 1.5 wt% of copper (Cu), 0.03 to 0.08 wt% Is introduced into a high-frequency vacuum induction furnace and is produced as an alloy according to a heating-up profile under an inert atmosphere. The method according to claim 6,
The method of the solder alloy after maintaining the inert atmosphere is a vacuum of a pressure of 3.0 × 10 ^-2 to 6.0 × 10 ^-2 torr, maintaining an inert atmosphere to 750 to 760 torr by purging with an inert gas. The method according to claim 6,
The heating profile includes a maintenance step after the first heating step and a maintenance step after the second heating step,
The primary heating temperature is 600 to 800 ° C,
Wherein the secondary heating temperature is 1000 to 1200 占 폚. The method according to claim 6,
The injected tin (Sn) is tin filtered impurities through vacuum refining,
Wherein the molten tin having a purity of 99.9% to 99.99% is put into a vacuum furnace to remove impurities having a higher vapor pressure and a lower boiling point than tin. The method according to claim 6,
The input tin (Sn) is a tin filtered through a filter,
Preparation of a solder alloy which is filtered tin in which impurity is removed by passing molten tin having a purity of 99.9% to 99.99% through a filter made of ferritic stainless steel or austenitic stainless steel with a hole having a diameter of 2 to 7 μm under a pressure of 3 to 4 bar Way. 1.5 to 2.5% by weight of silver (Ag);
0.5 to 1.5% by weight of copper (Cu);
0.03 to 0.08% by weight of nickel (Ni);
0.01 to 0.07% by weight of palladium (Pd); And
Tin (Sn) containing any inevitable impurities of the remainder. 12. The method of claim 11,
When the solder ball is reflowed to a printed circuit board electroplated with nickel (Ni) / gold (Au)
A first intermetallic compound layer containing (Cu, Ni) ₆ Sn ₅ is formed on the printed circuit board electroplated with nickel (Ni) / gold (Au)
Wherein a drop impact strength is increased by suppressing the formation of a second intermetallic compound layer containing (Ni, Cu) ₃ Sn ₄ on the first intermetallic compound layer. 12. The method of claim 11,
When the solder ball is reflowed to a printed circuit board which is electroless plated with nickel (Ni) / gold (Au)
Wherein a drop impact strength is increased by suppressing the formation of a dark layer including Ni ₃ P on a printed circuit board which is electroless plated with nickel (Ni) / gold (Au). (Cu), 0.03 to 0.08 wt.% Of nickel (Ni), 0.01 to 0.07 wt.% Of palladium (Pd), the remainder of tin (Sn), 1.5 to 2.5 wt.% Of silver, 0.5 to 1.5 wt. And a solder alloy including any unavoidable impurities is melted in a molten metal, and a master alloy is supplied and held, followed by induction heating and passing through an orifice hole to produce a ball of a predetermined size. 15. The method of claim 14,
Wherein the melting temperature is 230 to 250 占 폚. 15. The method of claim 14,
The master alloy is a Sn-Ge master alloy,
Wherein the holding temperature is 250 to 280 DEG C. 15. The method of claim 14,
Wherein the orifice hole is adjustable in frequency and pressure to adjust a size of a ball to be manufactured.

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