Soldering paste for connecting column

Abstract

The purpose of one aspect of the present invention is to provide a solder paste for a connection post, which has excellent connection reliability when a connection pin is connected to a semiconductor and other members. The present invention relates to a solder paste for a connection post, comprising a tin-containing powder having a particle size median of 3-5 [mu] m, a solder powder in which the proportion of powder having a particle size of 8 [mu] m or more is less than 1 wt%, and a flux for improving the wettability of the solder powder.

Description

Technical Field

[0001] The present invention relates to solder paste for connecting pillars, and more particularly, to solder paste for electrically connecting metal pillars having electrical conductivity and used for electrical connection to electrodes or substrates.

[0002] The present invention relates to a connection column, and more particularly, to a metal column having electrical conductivity and used for electrical connection, or a solder column having a solder layer on the metal column.

[0003] The present invention relates to semiconductor packages, and more particularly, to semiconductor packages including high aspect ratio connecting pillars. Background Art

[0004] As the pitch of electrodes continues to shrink, new concepts need to be developed for connection materials in semiconductor assembly. Therefore, research is underway to achieve stable connections using connection materials in metal shapes, such as metal pillars or conductive solder pillars with a solder layer plated on metal pillars for electrical connection.

[0005] When metal pillars or solder pillars are used, they can be used without the risk of bridging even if the pitch is reduced, and since the metal pillars or solder pillars are made of metal with high thermal conductivity, they also have a heat dissipation effect of dissipating the heat generated by the semiconductor to the substrate.

[0006] On the other hand, a method for forming a copper pillar for vertically connecting a bottom die and a top die is known in a stacked package structure of a certain package on package (PoP) structure, but the method for forming the copper pillar is stacking from the inside by electroplating, while the metal pillar manufactured from the outside and the manufacturing method thereof, the conductive solder pillar coated with a solder layer on the metal pillar and the manufacturing method thereof, the transmission method of the connecting pillar, the connecting method of the connecting pillar, etc. have not been studied in detail, and therefore there is an urgent need to develop technology in this area.

[0007] Furthermore, in order to use connection columns with a high aspect ratio in semiconductor connections, it is also necessary to develop specific paste combinations with high connection stability.

[0008]

Prior technical literature

[0009] (Patent Document 1) Korean Publication No. 10-2007-0101157. Summary of the invention

[0010] One aspect of the present invention is to provide a solder paste for a connection column that has excellent connection reliability when a connection needle is connected to a semiconductor or other components.

[0011] Another object of the present invention is to provide a connection column having excellent electrical conductivity and thermal conductivity and excellent connection reliability even at a high aspect ratio.

[0012] Another aspect of the present invention is to provide a semiconductor package including a connection column and having a novel structure with excellent connection reliability.

[0013] The solder paste for connecting columns of the present invention is characterized by comprising solder powder, the median value of the particle size of the solder powder is 3 to 5 μm, and the proportion of powder above 8 μm does not exceed 1% by weight; and flux for improving the wettability of the solder powder.

[0014] The solder paste for connecting columns of the present invention is characterized in that the portion of the powder with a particle size smaller than 1 μm does not exceed 10% by weight.

[0015] The solder paste for connecting columns of the present invention is characterized in that the oxygen concentration of the powder is below 800 ppm.

[0016] The solder paste for connecting columns of the present invention is characterized in that the flux accounts for 10 to 20 weight % of the total weight.

[0017] The solder paste for connecting columns of the present invention is characterized in that the flux comprises a solvent, a surfactant, an activator, an amine activator and an additive.

[0018] The solder paste for connecting columns of the present invention is characterized in that the amine-based activator contains at least one or more of triethanolamine, diethanolamine, tetraethylenediamine and polyoxyethylene tallow amine.

[0019] The solder paste for connecting columns of the present invention is characterized in that the ratio of the amine-based activator to 100 parts by weight of the solvent is 120 to 150 parts by weight.

[0020] The solder paste for connecting columns of the present invention is characterized in that the activator comprises an organic acid as a first activator and a halogen compound as a second activator.

[0021] The solder paste for connecting columns of the present invention is characterized in that the halogen compound is a bromine compound.

[0022] The solder paste for connecting columns of the present invention is characterized in that the bromine compounds are hexadecyltrimethylammonium bromide and trans-2,3-dibromo-2-butene-1,4-diol.

[0023] The solder paste for connecting columns of the present invention is characterized in that the halogen compound is an iodine compound.

[0024] The solder paste for connecting columns of the present invention is characterized in that the iodine compounds are 2-iodobenzoic acid and 3,5-diiodosalicylic acid.

[0025] The solder paste for connecting columns of the present invention is characterized in that the flux also additionally contains a de-flux agent for reducing residues, and the de-flux agent includes at least one or more of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, butyl carbitol, hexyl carbitol, and diethylene glycol diethyl ether.

[0026] The solder paste for connecting columns of the present invention is characterized in that the CV value of the solder powder is 40 to 50%.

[0027] The solder paste for connecting columns of the present invention is characterized in that the surfactant is one of propylene glycol ether, ethylene glycol ether, diethylene glycol ether, triethylene glycol ether and ethylene glycol ether acetate.

[0028] According to one aspect of the present invention, the solder paste for connecting pins can improve the corrosion and curing problems of the solder paste that occur during the installation process of the connecting pins, and provide excellent welding quality due to the appropriate composition. Therefore, this invention can significantly reduce the defective rate in the semiconductor connection process and improve the electrical reliability of the product. In addition, it can improve the productivity and cost saving of semiconductor manufacturing, and ensure the stability and accuracy of the manufacturing process.

[0029] In addition, according to another aspect of the present invention, the connecting column has excellent electrical conductivity and thermal conductivity, and still has excellent connection reliability under high aspect ratio. And compared with the traditional connecting parts, the volume of the solder layer is reduced, so the thermal conductivity of the connecting column is higher, so that the generated heat energy is dissipated to the substrate, which has a heat dissipation effect.

[0030] Furthermore, according to the semiconductor package of the present invention, although the connection material is disposed in a narrow area, tilt, missing, reduction in shear strength and lack of fusion of the connection material do not occur, the defect rate is reduced, and the electrical reliability of the product is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a cross-sectional view of a solder column.

[0032] Figure 2 Schematic diagram of various shapes of solder pillars according to various embodiments of the present invention.

[0033] Figures 3 to 7 The present invention describes an implementation form of a semiconductor package.

[0034] Figure 8 A manufacturing method is described in which, in a step of mounting a semiconductor chip, a first surface of a semiconductor chip where terminals are formed is bonded as a connection surface and a manufacturing method in which a reverse surface where terminals are formed is bonded to the first connection surface.

[0035] Fig. 9 It is a diagram describing the inclination of the connecting column.

[0036] Fig.10 The photographs show the degree of inclination and missing of Example 3 and Comparative Example 3.

[0037] Fig.11 and Fig.12 The particle size distribution diagram of the solder powder used in Example 3 and Comparative Example 3 is shown.

[0038] Fig.13 This is an electron microscope photo taken after the connection pillars were connected to the connection surface using solder paste.

[0039] Fig.14 This is an electron microscope photograph of the solder joint thickness between the connection column and the connection surface measured using the three-point measurement method.

[0040] Fig.15 These are photographs for confirming the tilt angle and the missing rate of Example 8 and Comparative Example 11.

[0041] Fig.16 These are photographs for confirming the tilt angle and the missing rate of Example 8 and Comparative Example 5.

[0042] Fig.17 These are photographs for confirming the tilt angles and voids of Example 8 and Comparative Example 7.

[0043] Fig.18 The photographs show the tilt angle and the missing rate caused by the formation of the solder layer in Example 9 and Example 10.

[0044] Fig.19 The photographs show the influence of the difference in edge R between Example 9 and Example 10 on the tilt angle.

[0045] Fig. 20 The photographs show the difference in the edge R value of Example 10 and Comparative Example 11 with respect to the tilt angle and the missing rate.

[0046] Fig.21 This is a defect confirmation photograph of Comparative Example 8 in which no plating layer is formed on the outside of the metal column.

[0047] Fig. 22 These are photos used for evaluation purposes.

[0048] Fig.23 This is a drawing showing photographs of weldability results of examples of Experimental Example 2 of the present invention.

[0049]

Explanation of symbols

[0050] 10: Metal pillar

[0051] 20: Solder layer

[0052] 30: Specific implementation of diffusion layer DETAILED DESCRIPTION

[0053] The present inventive concept described below may be subjected to various transformations and may have various embodiments, specific embodiments are illustrated in the figures, and detailed descriptions are given in detail. However, this does not mean to limit the present inventive concept to a specific implementation form, and should be understood to include all transformations, equivalents or substitutes within the technical scope of the present inventive concept.

[0054] The terms used below are only used to describe specific embodiments and are not intended to limit the present inventive ideas. Singular expressions include plural expressions unless the context clearly means otherwise. In the following, the terms "including" or "having" indicate that the features, numbers, steps, operations, components, parts, ingredients, materials or combinations thereof listed in the specification exist without excluding in advance the possibility of the existence of one or more other features, numbers, steps, operations, components, parts, ingredients, materials or combinations thereof.

[0055] In order to clearly represent the various layers and regions in the drawings, their thickness may be enlarged or reduced. Throughout the specification, the same graphic code is used for similar parts. Throughout the specification, when a layer, film, region, plate, etc. is said to be "above" or "on" other parts, this includes not only being directly above it, but also having other parts between it. Throughout the specification, terms such as first, second, etc. can be used to describe various components, but components should not be limited by these terms. These terms are only used to distinguish one component from another component.

[0056] Although the terms first, second, etc. are used to describe various elements, components, regions, layers and / or regions, it should be understood that these elements, components, regions, layers and / or regions should not be limited by these terms.

[0057] In addition, the processes described in the present invention do not mean that they must be applied in order. For example, if there is a first step and a second step, it does not mean that the first step must be performed before the second step.

[0058] The metal in this specification refers not only to metal elements but also to metals in a common sense, such as metal alloys.

[0059] The metal column in this specification is a columnar connector used for connection, and its exterior is not separately provided with a solder layer.

[0060] The solder column in this specification is used to connect with an electrode or substrate, etc., and an undefined columnar connector with a solder layer separately provided on the outer surface of the metal column. At this time, the solder layer will flow during reflow, so that both ends of the metal column can be fixed.

[0061] The connection column in this specification includes the aforementioned metal column and solder column, and is a concept of a columnar connection member for electrical connection that performs electrical connection in a semiconductor package.

[0062] <First aspect> Solder paste for connecting column

[0063] According to this aspect, the solder paste for connecting pillars can be used for semiconductor packaging, particularly for connecting both ends of a metal pillar to electrodes or a substrate on a semiconductor package, or for forming a solder layer on the outside of the metal pillar.

[0064] The solder paste of this embodiment includes solder powder and flux.

[0065] Solder powder is a powder containing tin, which can actually melt to become an electrical connection medium. Solder powder is the main component of preparing solder paste, mainly made of metal alloys, in this regard, it is composed of lead-free low melting point metals.

[0066] The particle size, shape and alloy composition of solder powder have a great influence on the quality and performance of solder paste. Particle size is very important because it determines the melting speed and adhesion of solder during the soldering process. Therefore, in the present invention, the mean particle size of solder powder is 3 to 5 μm.

[0067] When the median particle size of the solder powder is less than 3μm, the overall micropowder content increases, resulting in an increase in the viscosity of the solder paste, thereby reducing the working performance; when the particle size is greater than 5μm, the rheology of the solder paste decreases, resulting in shape collapse during printing.

[0068] In addition, the portion of the solder powder with a diameter less than 1 μm should be less than 10% by weight, and more preferably between 3% and 10% by weight. If the weight of the solder powder is less than 3%, the viscosity of the solder paste will increase, which may cause printing defects. If the micropowder less than 1 μm exceeds 10% by weight, the surface area of ​​the solder powder increases and the oxide film cannot be completely removed, which may cause incomplete melting during the reflow process.

[0069] In addition, the weight of the solder powder with a diameter of 8 μm or more in the solder paste should be less than 1 wt %. If the weight of the coarse powder with a diameter of 8 μm or more exceeds 1 wt %, a tilt defect may be caused when mounting the Cu column.

[0070] Solder powder must contain tin and can be selected from silver and copper, and its melting point is ideally 217°C to 220°C.

[0071] Specific examples include Sn-Ag-Cu, Sn96.5Ag3.0Cu0.5.

[0072] To prevent incomplete melting and tilting, the CV value of solder powder is preferably between 30 and 40. When it exceeds 40%, tilting defects may occur due to the large difference between coarse powder and fine powder, especially when there is more coarse powder, printing omissions and printing template clogging may occur.

[0073] The oxygen concentration of the solder powder used is preferably less than 800 ppm. When the oxygen concentration exceeds 800 ppm, the solder powder surface is oxidized and incompletely melted, which may cause the connection performance to deteriorate and cause reliability problems.

[0074] The flux melts along with the solder powder during the soldering process, reacts with oxygen exposed to the air, and prevents oxidation, thereby achieving a clean, stable electrical connection between the solder and the component. In addition, the flux cleans the surface of the component, removes impurities, grease, and other external contaminants, and improves the "wettability" of the solder.

[0075] The content of flux is preferably 10% to 20%. When the content of flux is less than 10%, since the solder powder is not completely melted, the solder powder may act as an impurity during the reflow process after the connection pin is installed, causing the connection pin to tilt, thereby making the electrical connection unstable.

[0076] When the flux content exceeds 20%, after the solder paste melts, voids may be generated due to unreacted flux, and the viscosity will be greatly reduced, resulting in a decrease in printing performance. In addition, due to the reduced adhesion of the solder paste, the metal column may easily fall off during installation, resulting in an increase in the missing rate.

[0077] At this time, the flux includes a surfactant, an activator, an additive and a solvent. The additive can be selectively used to remove the flux, and it is best to use a water-soluble flux. The water-soluble flux provides high yield and a clean surface.

[0078] Surfactant is a component that is soluble in both water and oil. It can be completely removed by water during the cleaning process after reflow, and can diffuse in a smaller space to promote the spreading of the solder surface and enhance adhesion. It can include one or more selected from the group consisting of propylene glycol ether (Propylene Glycol Ether), ethylene glycol ether (Ethylene Glycol Ether), diethylene glycol ether (Diethylene Glycol Ether), triethylene glycol ether (Triethylene Glycol Ether) and ethylene glycol ether acetate (Ethylene Glycol Ether Acetates).

[0079] In particular, Propylene Glycol Ether has a low surface tension, which allows the solder paste to spread well on the surface of the object, can adjust the drying time, and improve the quality of the solder joint.

[0080] Activators are used to remove the oxide layer on the surface of copper needles, solder powder and substrates (Pads), provide better wettability between solder and electrodes, etc., and prevent them from re-oxidation at high temperatures, thereby protecting their surfaces.

[0081] In the present invention, the activator includes a first activator, a second activator and a third activator.

[0082] The first activator is mainly an organic acid used to remove the oxide film of the pad and the copper column (Cu column), and an organic carboxylic acid is an ideal choice. For example, one or more acids selected from the group consisting of succinic acid, glutaric acid, lauric acid, sebacic acid, adipic acid, suberic acid, and maleic acid can be selected.

[0083] The content of the first activator in the entire soldering flux is preferably 2 to 7 wt %.

[0084] If the content of the organic acid is below the above range, the oxide film may not be completely removed, which may result in non-melting, which may cause tilting and missing. If the organic acid exceeds the above range, the metal and organic acid in the solder paste may react to form a metal salt before the reflow process, which may cause the solder paste to harden and corrode.

[0085] In addition, in order to provide stronger activity, the activator can further include a halogen compound as a second activator, including a chlorine compound, a fluorine compound, an iodine compound and a bromine compound. Chlorine compounds include chloroacetate, chloropyridine and chloroacrylate. Fluorine compounds include fluorinated amines, fluorinated ethylene and ammonium fluoride. Iodine compounds include 2-iodobenzoic acid and 3,5-diiodosalicylic acid. Bromine compounds include cetyltrimethylammonium bromide and trans-2,3-dibromo-2-butene-1,4-diol.

[0086] In the embodiments of the present invention, bromine compounds are used, and due to their higher activity and lower evaporation temperature, the paste is more easily volatilized during the assembly process, better fills the space between components, and achieves excellent welding.

[0087] The third activator is an amine-based activator, and at least one amine selected from the group consisting of triethanolamine, diethanolamine, tetraethylenediamine, and polyoxyethylene alcoholamine can be selected. The amine-based activator allows the flux (soldering flux) to better contact the surface of the connecting column and spread better on a smaller connecting surface.

[0088] The solvent is used to enhance the interface between the solder and the connection column, and may include one or more solvents selected from the group consisting of terpineol, menthol, dipentene, and limonene.

[0089] In the soldering flux, based on 100 parts by weight of the solvent, the surfactant is preferably 110 to 150 parts by weight, the activator is 10 to 20 parts by weight, the amine activator is 120 to 150 parts by weight, and the additive is 2 to 10 parts by weight.

[0090] If the surfactant exceeds the above range, excessive bubbles may be generated in the flux, causing printing abnormalities. Excessive reduction in surface tension may cause the flux to spread in unnecessary areas.

[0091] If the surfactant is below the above range, the cleaning process after reflow may leave residues and the flux may not spread in the desired manner.

[0092] Activators exceeding the above range may cause undesirable chemical reactions or reduce the stability and durability of the flux. Below this range, sufficient chemical reactions may not occur, resulting in reduced adhesion or soldering quality.

[0093] If the amine-based activator exceeds the above range, the pH balance of the flux may be disrupted, an undesirable corrosion reaction may occur, or the stability of the flux may decrease.

[0094] If the amine activator is below the above range, the humidity, dispersibility, oxidation resistance, etc. of the flux may be weakened and the overall performance may be reduced.

[0095] If the additive exceeds the above range, the chemical stability of the flux may decrease, or some specific properties may be over-enhanced, resulting in the destruction of other important properties. Below this range, some properties or characteristics of the flux may not be fully exerted, which may lead to a decrease in the overall performance of the flux.

[0096] Defluxing is used to remove residual flux after the soldering process. After the soldering process, if the flux remains on the components or circuits, it may cause corrosion, changes in electrical properties, thermal problems and surface contamination. Therefore, it is appropriate to use a defluxing agent that helps remove flux, prevents oxidation and corrosion.

[0097] Therefore, modified glycol ethers (such as ethylene glycol (Ethylene Glycol), propylene glycol (Propylene Glycol), diethylene glycol (Diethylene Glycol), triethylene glycol (Triethylene Glycol), polyethylene glycol (Polyethylene Glycol), butyl carbitol (Butyl Carbitol), hexyl carbitol (Hexyl Carbitol), diethylene glycol diethyl ether (Diethylene Glycol Diethyl Ether)) can be used as de-flux agents.

[0098] <Second Aspect> Connecting Column

[0099] The second aspect of the present invention is a connection column, which includes a metal column and a solder column formed on the outside of the metal column.

[0100] In the present invention, the metal pillar is a columnar metal pillar made by cutting a metal wire and forming it into a predetermined diameter and height. In an embodiment of the present invention, the metal pillar is a connecting metal pillar for electrically connecting a substrate and a substrate, a substrate and a pad or an electrode on a semiconductor chip, and the conductivity of the connecting metal pillar is 11 to 101% IACS, and it is desirable to have high conductivity.

[0101] In order to have the above-mentioned electrical conductivity, the connection metal column includes at least one metal selected from the group consisting mainly of Cu, Ag, Au, Pt, and Pd.

[0102] Furthermore, when the connection metal column in this embodiment is used as the connection material, its thermal conductivity is 50 to 450 W / mK, preferably 320 to 450 W / mK. This is because such a connection material can have a heat dissipation effect by conducting heat toward the substrate.

[0103] In addition, the Vickers hardness of the metal column of this embodiment is preferably 160 to 300 HV. If it exceeds the above range, it is difficult to cut when making the column, and problems such as breakage or bending may occur. If it is lower than this range, burrs may appear on the cut surface.

[0104] The metal pillar has a diameter of 60 to 500 μm, preferably 50 to 300 μm, and a height of 60 to 3,000 μm, preferably 60 to 1,000 μm.

[0105] The above diameter and height are selected in consideration of mechanical stability, bonding strength, manufacturing process and thermal management. If it is lower than the above range, the impedance of the electrical connection may increase, which may limit the flow of electrical signals, which may lead to reduced electrical performance, reduced structural strength, failure to provide sufficient mechanical strength, and failure to maintain reliability against external shock or vibration.

[0106] In addition, small diameter metal pillars may limit heat dissipation. Heat generated in semiconductor devices should be properly dispersed. If the diameter of the metal pillar is too small, the heat may not be sufficiently dispersed, and semiconductor overheating problems may occur. If the diameter is small, precise assembly and manufacturing may be difficult.

[0107] On the one hand, when the diameter of the metal pillar exceeds the above range, it occupies the limited space inside the semiconductor chip, resulting in space restrictions in chip design and may cause collision or interference with other components or contact points. The dispersion of current is restricted, which may cause temperature rise or electrical problems.

[0108] The aspect ratio (length / diameter) of the metal pillar is preferably 1 to 10. Particularly in the present invention, when manufactured by cutting metal wire, metal pillars with an aspect ratio of 3 to 5 for multi-chip packages having narrow pitches and high substrate-to-substrate heights can be manufactured.

[0109] The aspect ratio is related to mechanical stability, bonding strength, manufacturing process and heat dissipation. From the perspective of mechanical stability, if the aspect ratio is less than the above range, the structural strength may be insufficient and may be sensitive to external shock or vibration. In addition, if it exceeds this range, the geometric stability may be reduced and problems such as bending or deformation may occur.

[0110] From the perspective of bonding strength, if the aspect ratio is smaller than the above range, it may not provide sufficient bonding area, while if the aspect ratio is larger, the bonding force may be reduced, which may affect the reliability of the component.

[0111] From the perspective of manufacturing process, if the aspect ratio is smaller than the above range, precise control and assembly are required, while if the aspect ratio exceeds this range, it may be difficult to effectively control during the manufacturing process.

[0112] From a thermal management perspective, if the aspect ratio is smaller than the above range, heat dissipation may be insufficient, while if the aspect ratio exceeds this range, thermal issues may occur due to heat transfer path restrictions.

[0113] When metal pillars are manufactured by cutting copper wires and used in semiconductor packaging, it becomes an important technical challenge to make the round surface of the metal pillar perpendicular to the ground. If it is not erected correctly, the metal pillar may tilt, be lost, be difficult to adhere, and the shape may be deformed during the adhesion process.

[0114] Therefore, when the metal column is erected on the bottom surface, the angles of all horizontal and vertical surfaces of the metal column are preferably within the range of 90±3°.

[0115] When the above range is exceeded, the metal column becomes sensitive to external shocks and vibrations, may tilt, increase the loss rate, and become difficult to accurately align with other components, and the shape of the metal column may be deformed during the attachment process.

[0116] In addition, the edge radius (edge ​​R) value of the metal column is between 3μm and 20μm, preferably in the range of 5μm to 10μm. The edge radius here refers to "edge radius" or "edge rounding", which indicates the degree of roundness of the edge. If it exceeds the above range, the connection surface of the metal column will become rounded, resulting in a tilt (Tilt) on the component. If it is less than the above range, the edge of the metal column may become sharp and pointed. This shape may cause the fillet at the bottom of the metal column to not be fully formed, and the solder paste may not fully adhere to the surface of the metal column.

[0117] In order to make the edge R value within the above range, soft etching may be performed using an oxidizing agent.

[0118] Nitric Acid or Sulfuric Acid with a concentration of 5% to 30% can be used as an oxidant. The treatment time varies from a few seconds to a few minutes depending on the diameter and length of the metal column. When using sulfuric acid, the treatment time is 2 / 3 of that of nitric acid solution.

[0119] The tensile strength of the metal column is preferably between 170 and 950 MPa. Exceeding this range may result in defects in the metal raw material supply, and below this range may cause the shape of the metal column to be flattened during manufacture.

[0120] The Vickers hardness of the metal column of this embodiment is 150 HV or more, preferably between 150 and 300 HV, and more preferably between 160 and 220 HV. In order to achieve the above hardness, it is preferable to perform the heat treatment described below.

[0121] In order to manufacture the metal column of the present invention, the typical production process of the metal wire is to first melt the metal and then supply it to a continuous casting device, where it solidifies to form a wire bundle. This wire bundle is then formed (depending on the application example, it may be rolled, pressed, drawn) to obtain a metal wire of a specified diameter.

[0122] Usually, the wire needs to have the highest possible electrical conductivity, so a high-purity copper melt can be used that excludes added elements as much as possible.

[0123] In order to reduce the composition of the additive element in the copper melt, one method is to set an appropriate oxygen content in the copper melt and solidify the additive element contained therein. As a result, part of the oxide of the additive element generated floats on the surface of the copper melt in the form of slag, so it can be removed.

[0124] However, copper wire made from high-purity copper melt has larger crystals due to the increased purity of the material, which leads to the problem of burrs on the cut surface when the copper wire is cut. Burrs can be defined as incomplete finishes that leave some copper in the cutting direction when the wiring is cut with a knife or the like.

[0125] That is to say, the metal pillar in this embodiment will inevitably generate burrs on the cutting surface when cutting the metal wire, and the length of the burrs generated at this time is preferably 0.1 μm to 0.5 μm or less.

[0126] When the wire is cut, if the burr of the metal column is larger than a certain size, the plating of the solder layer becomes difficult, and it must be used upright in the semiconductor package, and cannot function as a connecting pin. Therefore, using a metal column with burrs in the above range can produce a metal column with excellent plating adhesion, plating thickness uniformity and minimized, thereby preventing tilting.

[0127] As an example of a metal column, a copper alloy column may be manufactured. The copper alloy column is a column structure cut from a copper alloy wire having copper as a main component and having a prescribed diameter and height, and contains copper and at least one additional element.

[0128] The electrical conductivity of pure copper needles with a purity of 99.9 or more is 99 to 101% IACS, which is very high. However, when copper needles are made of pure copper alone, burrs will be generated on the cut surface when cutting the wire due to its high ductility, so additional elements need to be added.

[0129] That is, by adding a specified amount of additional elements to copper, the mechanical properties that determine the crystal grain size can be made smaller when the copper is melted. Therefore, the copper alloy wire containing the additional elements increases the strength and hardness of the material, and the surface becomes harder, thereby minimizing the burrs on the cut surface.

[0130] The additional element is mainly at least one selected from the group consisting of Sn, Fe, Zn, Mn, Ni, and P, and it preferably contains 0.1wt% to 20wt%, and more preferably 5 to 10wt%. If it is lower than this range, there will be too many burrs on the cutting surface, and if it exceeds this range, the conductivity will decrease.

[0131] More preferably, the additional element may include about 0.0.5 to 20 wt% Sn (better 2 to 10 wt%), and may be mixed with Zn in a ratio of 1:1 to 100:1 (better 1:1 to 10:1). Since Sn can improve the strength and hardness of the material, and Zn can improve its corrosion resistance and wear resistance, when they are mixed in the above ratio, the generation of burrs can be minimized. In addition, in order to further improve corrosion resistance and reliability, 0.01 to 1 wt% P and 0.01 to 10 wt% Pt or Pd may be added as additional elements.

[0132] On the other hand, as described later, if only metal pillars without a solder layer are used, the aforementioned solder paste needs to be provided on the connection surface to achieve connection.

[0133] Figure 1 A solder column is a column that has formed a solder layer. The solder column includes the outside of the aforementioned metal column and the solder layer. The solder layer is provided in at least one area outside the metal column. When the solder layer melts, the top of the solder column is connected to the substrate or chip at the bottom, and a solder joint can be formed. In addition, a diffusion layer (30) described later may be included between the metal column and the solder layer.

[0134] The solder layer (20) is plated on the metal column, so the metal column needs to have good gold plating properties. In addition, compared with traditional solder balls, the solder column has a smaller connection area in contact with the substrate, so in the reflow process of pasting the solder layer on the printed circuit board, the solder column may not stick to the electrode or the substrate, resulting in a large number of missing phenomena, and the working performance may be greatly reduced. Therefore, the solder column needs to meet the thermal shock performance and accelerated shock performance of the solder connection part, and at the same time requires a high degree of reliability enhancement.

[0135] On the other hand, according to one embodiment of the present invention, due to regulations on the use of lead (Pb) caused by environmental pollution, the solder layer is based on an element having physical properties similar to those of lead, namely, tin (Sn) having excellent conductivity, ductility, corrosion resistance and castability.

[0136] However, in order to meet the properties required of the solder layer, such as gold plating, drop impact (Drop strength) strength, thermal cycling (TC) characteristics and wettability (Wet-ability), it is more appropriate to use a method of alloying with other metals rather than using only tin to form the solder layer.

[0137] Therefore, the solder layer of the present invention is more suitable for alloying tin (Sn) with silver (Ag) and copper (Cu) to form a Sn-Ag-Cu alloy for high electrical and thermal conductivity, wherein silver (Ag), copper (Cu) and the remaining tin and any inevitable impurities can be well attached to the copper alloy pin before reflow, and the reliability of the connection can be ensured after reflow.

[0138] More specifically, a solder alloy comprising 1.5 to 4.0 wt % of silver (Ag), 0.2 to 2.0 wt % of copper (Cu), the remaining tin (Sn) and any unavoidable impurities is provided. The solder column manufactured using this alloy performs well in drop impact strength, thermal cycling (TC) characteristics and wettability, and can provide a low Missing rate effect.

[0139] Let's look at the various components of the solder layer. Silver (Ag) itself is non-toxic and can increase the melting point of the alloy, improve the wettability of the connection material, reduce resistance, and improve thermal cycling (TC) characteristics and corrosion resistance.

[0140] The silver (Ag) content in the solder layer is preferably 1.5 to 4.0% by weight. If the silver (Ag) content is less than 1.5% by weight, it is difficult to fully ensure the electrical conductivity and thermal conductivity of the solder layer, and the wettability will be reduced. If it exceeds 4.0% by weight, a bulky IMC called Ag3Sn will form inside the solder alloy and the solder layer, and the impact resistance of the solder will be impaired due to the excessive growth of the bulky IMC. The best content is 2.2 to 3.2% by weight, and more preferably 3.0% by weight.

[0141] Copper (Cu) can affect the connection strength or tensile strength, thereby improving the drop impact (Drop) characteristics. The copper (Cu) content in the solder layer is preferably 0.2 to 2.0% by weight. If the copper (Cu) content is less than 0.2% by weight, it is difficult to enhance the connection strength or tensile strength of the solder layer. If it exceeds 2.0% by weight, the solder will become hard, prone to tissue damage, and may reduce its processability. The best content is 0.2 to 1.0% by weight, and more preferably 0.5% by weight.

[0142] Zinc may be added selectively. When the content of zinc (Zn) is 0.1 to 0.7%, it can prevent the formation of Bulky IMC, thereby improving weldability.

[0143] The metal post should ideally have a melting point of 500 to 1000° C. If it exceeds this range, the manufacturing cost increases, and if it is below this range, the metal post may melt during the connection process.

[0144] The ideal thickness of the solder layer is 0.1 to 10μm and is formed by a plating process. If the plating thickness of the solder layer exceeds 10μm, the solder layer may be excessively melted into a liquid state during the reflow process and flow down along the metal pillar and gather around the metal pillar. This will reduce the stability of the metal pillar due to the unstable state of the solder layer and may cause the metal pillar to bend or fall off.

[0145] In addition, if the plating thickness is kept above 10μm, the risk of void formation may increase. That is, thicker plating may make it easier for the solder paste to contain air when interacting with the metal pillar.

[0146] When the plating thickness of the solder layer is less than 0.1 μm, its anti-oxidation effect on the metal pillar may be insufficient, which may lead to reduced electrical performance. In addition, the solder layer can increase the surface tension and make the solder paste gather around the metal pillar, but if the solder layer is too thin, it may not be fully affected by the surface tension, which may limit the distribution and stability of the solder paste.

[0147] On the other hand, when soldering is performed at both ends of the solder column using a solder layer with the same composition as the solder paste, such as SAC305, since the composition of the plating layer and the solder paste is the same, there will be no interface problems between the solder column and the solder paste, such as voids, lattice mismatch, poor wettability, interface cracks, etc., and it has an excellent wettability effect.

[0148] Furthermore, the solder layer melts during the reflow process, generating surface tension, which allows the metal pillars to be mounted vertically and exhibit a self-alignment effect. Therefore, if the plating thickness of the solder layer is less than 0.1 μm, the risk of interface problems and tilting problems may increase.

[0149] The solder layer plating method can use barrel plating and electroless plating, and go through the steps of pouring, gold plating and cleaning.

[0150] The melting point of the solder layer is preferably between 200 and 250°C. If it exceeds 250°C, problems may occur due to damage to electronic products; while below 200°C, the product may re-melt during use.

[0151] The solder layer is formed on at least one region of the metal pillar, and its shape is not limited. Figure 2 Various shapes of solder pillars according to various embodiments of the present invention are shown. Accordingly, the solder pillars can form solder layers on the side, or form solder layers on the upper and lower parts, or form solder layers along the upper and lower sides according to the application.

[0152] Even if there is no solder paste on the connection surface, the connection can be made as long as flux is applied, but it is better to provide a solder layer (20) under the metal column (10), which is beneficial in some packaging processes. The thermal conductivity of the solder layer is preferably 50 to 80W / mK.

[0153] On the other hand, Figure 1 As shown, a diffusion layer (30) may be provided between the metal column and the solder layer. The diffusion layer is a plating layer introduced to prevent the metal alloy atoms contained in the metal column and the tin or other metal atoms of the solder layer from diffusing and forming intermetallic compounds. The diffusion layer includes metal atoms in the metal column and a solid solution region formed by diffusion at high temperature. Ideally, when copper is used as the first metal, the diffusion layer should contain nickel having the same or similar crystal structure and a small difference in atomic size. For example, nickel (Ni), Ni-Ag, Ni-P, Ni-B, Co, etc. may be used.

[0154] In order to improve the electrical and thermal conductivity of the solder column, it is best to form the diffusion layer plating to 50 to 100 W / mK, in which case Ni-Ag is an ideal choice.

[0155] The method for manufacturing a solder column according to the present invention will be described below. The method for manufacturing a solder column includes a melting process, an extrusion and molding process, a cutting process, and a solder layer forming process.

[0156] The melting step is a step of melting a specific component of additive elements contained in a molten metal.

[0157] Extrusion and forming processes are steps to produce strands or sheets by rolling, pressing or drawing.

[0158] The wire drawing process is a step of forming a stranded wire or a thin plate into a wire having a predetermined diameter.

[0159] The heat treatment process is a heat treatment step to ensure the strength of the components. The heat treatment is preferably performed at a temperature above 160 degrees and below 300 degrees. Through heat treatment, the ideal hardness of 150 to 300 HV can be obtained. If it exceeds this hardness, the hardness is too high, making it difficult to cut or it may break; if it is lower than this hardness, the size of the burr or the increase in yield will occur.

[0160] The cutting process is a step of cutting the stretched copper wire into a specified length in the wire drawing process. At this time, it is best to use the die cutting method for cutting. The die cutting method uses a press process to insert the metal wire into a die inside the press and cut it at a fixed pitch at high speed to produce metal columns. According to the above method, the metal wire is stretched and produced with a specified composition. After heat treatment to make the Vickers hardness of the metal wire reach 150 to 300 HV, it is cut by the die cutting method to minimize the generation of burrs.

[0161] The solder layer forming process is a step of forming an electroplated layer by electroplating a metal containing Sn on the surface of the metal core. Electrolysis is to put the metal core into a barrel, put the plated metal on the anode, and hang the plated object on the cathode in the barrel for electrolytic plating. At this time, keep the temperature at 20-30℃. Select the appropriate electroplating time according to the size.

[0162] The material of the solder plating solution may be an alloy containing Sn, such as SnAg, SnAgCu, SnCu, SnZn, SnMg, SnAl, etc. Sn-Ag-Cu is an ideal choice, and at this time, the content of copper (Cu) is 0.2 to 2.0 weight %.

[0163] When the content of copper (Cu) is less than 0.2 wt%, it is difficult to improve the bonding strength or tensile strength of the solder layer. When the content exceeds 2.0 wt%, the solder will harden, the structure will be easily damaged, and the processability will be reduced. The optimal range is 0.2 to 1.0 wt%, and more preferably 0.5 wt%. The optimal content of Ag is 1.5 to 4.0 wt%.

[0164] When the content of silver (Ag) is less than 1.5 wt%, it is difficult to fully ensure the electrical conductivity and thermal conductivity of the solder layer, and its wettability is reduced. When its content exceeds 4.0 wt%, a bulky IMC called Ag3Sn will form inside the solder alloy and solder layer, and the impact resistance of the solder will be impaired due to the excessive growth of the bulky IMC. The electrolyte used for electroplating is preferably a methanesulfonic acid series solution.

[0165] Furthermore, before forming the solder layer, a pretreatment step and a diffusion layer forming step may be included.

[0166] The pretreatment process includes a degreasing process to remove organic matter or impurities on the surface of the metal column, and a pickling process to remove the oxide layer on the surface of the metal column. The pretreatment process is necessary because the organic matter, impurities or oxide layer on the surface of the metal column may hinder the formation of the plating layer.

[0167] The diffusion layer formation process is a non-electroplating layer formed directly on the surface of the metal column after the pretreatment process. It can prevent oxidation and the resulting wetting defects on the copper pad and the metal column, and improve the bonding strength and reliability by producing (Cu, Ni)6Sn5 intermetallic compounds to replace the Cu6Sn5 intermetallic compound bonding layer.

[0168] The composition of the diffusion layer formed on the surface of the solder column is not particularly limited, but nickel (Ni), Ni-Ag, Ni-P, Ni-B, Co, etc. can be used. Considering thermal conductivity, Ni-Ag is the best choice. The diffusion layer can usually be formed by a well-known electroplating method. If the diffusion layer is formed by an electroless plating method, there may be problems in thickness and reliability.

[0169] The thickness of the solder layer ranges from 1 to 10μm, more preferably 1 to 7μm, 1 to 5μm, and 1 to 3μm, depending on the diameter of the metal column. If the solder layer exceeds the above range, it may tilt during soldering, or the amount of solder may be too much, causing bridging and reducing thermal conductivity. If it is less than the above range, poor soldering may occur due to insufficient solder. If the solder layer exceeds the above range, it may tilt during soldering, or the amount of solder may be too much, causing bridging and reducing thermal conductivity. If it is less than the above range, poor soldering may occur due to insufficient solder.

[0170] The thickness of the diffusion layer is preferably 0 to 5 μm. That is, the diffusion layer can be selectively included, but it is better to include it. When the diffusion layer is included, a thickness of 1 to 5 μm, 1 to 3 μm can be formed by electroplating, and the thickness of the diffusion layer is preferably thinner than the solder layer. If the above range is exceeded, the bonding layer of the pad, metal column, and solder may be at risk of early cracking due to the formation of Kirkendall voids under heat sources (including temperatures of around 150 degrees), and Cu consumption may occur under long-term heat treatment or exposure to thermal cycles / thermal shocks.

[0171] It is also possible to form a diffusion layer of 0.1 to 1 μm using an electroless plating method, but depending on the conditions, there may be a risk of early cracking due to Kirkendall voids, and Cu consumption may occur during long-term heat treatment or exposure to thermal cycling / thermal shock.

[0172] In addition, the thermal conductivity of the metal column is 50 to 450 W / mK, more preferably 320 to 450 W / mK, the thermal conductivity of the solder layer is 50 to 80 W / mK, and the thermal conductivity of the diffusion layer is 50 to 100 W / mK. In particular, since the solder column has a small heat transfer area and a long heat transfer thickness, the thickness of the solder layer should be as thin as possible to maintain a high thermal conductivity of the entire solder column.

[0173] <Third Aspect> Semiconductor package and method of manufacturing the same

[0174] A third aspect of the present invention provides a semiconductor package. The semiconductor package structure of this aspect includes a first connection surface, a second connection surface, a connection column and a solder joint.

[0175] The first connection surface and the second connection surface may be electrical connection surfaces such as electrodes, pads, terminals, wirings, bumps, etc. on a connection body such as a PCB, an interposer, an RDL, a substrate, a film, a semiconductor chip, etc., according to various forms of the structure of the semiconductor package. The first connection surface and the second connection surface may be connection surfaces of the same type, but usually they are different.

[0176] The connecting pillars have a diameter of 60 to 500 microns, more preferably 50 to 300 microns, and a height of 60 to 3,000 microns, more preferably 60 to 1,000 microns.

[0177] The connection pillar may be composed of the aforementioned metal pillar or solder pillar, and the aspect ratio of the connection pillar is preferably 1 to 10.

[0178] The aspect ratio is a factor related to mechanical stability, bonding strength, manufacturing process, and heat dissipation. From the perspective of mechanical stability, if the aspect ratio is below the above range, the structural strength may be insufficient and may be sensitive to external shock or vibration. In addition, if it exceeds this range, the geometric stability may be reduced and problems such as bending or deformation may occur.

[0179] Furthermore, from the perspective of bonding strength, if the aspect ratio is below the above range, a sufficient bonding area may not be provided, and if the aspect ratio is above the above range, the bonding force may be reduced, which may cause reliability problems of the assembly.

[0180] In addition, from the perspective of the manufacturing process, if the aspect ratio is lower than the above range, precise control and assembly may be required, while if the aspect ratio is higher than the above range, it may be difficult to effectively control during the manufacturing process.

[0181] Furthermore, from a thermal management perspective, if the aspect ratio is below the above range, sufficient heat dissipation may not be provided, and if the aspect ratio is above the above range, thermal problems may occur due to the limitation of the heat conduction path.

[0182] Furthermore, when the connecting pillar is perpendicular to the first connecting surface or the second connecting surface, the angle between the connecting pillar and the first connecting surface or the second connecting surface may not be perpendicular.

[0183] That is, when mounting in combination with solder paste, the connection pillars may not be arranged vertically due to the aforementioned edge R, the angles of the vertical and horizontal planes, etc., which is called the degree of tilting.

[0184] The degree of tilting indicates the angle difference between the line between the center point of the connecting column hardened and fixed after welding and the connecting surface and the vertical line of the connecting surface. If the tilting exceeds a certain range, the component may not work properly. The degree of tilting (θ) is preferably within 4°.

[0185] The surface roughness of the connecting column is preferably between RMS 0.5 and 1μm. When the RMS value of the surface roughness is less than 0.5μm, it may cause insufficient distribution and adsorption of the liquid. A too smooth surface may cause the liquid to slide on the surface, reducing its stability, which means that the solder paste may not be evenly distributed and adequately adsorbed on the surface of the connecting column, which may weaken the bond between the solder paste and the connecting column, and therefore, may become sensitive to mechanical shock or temperature changes.

[0186] When the RMS value of the surface roughness exceeds 1μm, the distribution of the liquid may be uneven. If the surface is too rough, the solder paste may concentrate more on the high points of the surface, resulting in uneven liquid distribution. This may cause excessive solder paste to accumulate around metal pillars or form an uneven coating on the surface.

[0187] Furthermore, quality issues may occur due to increased surface tension. A rough surface may increase surface tension, which can restrict the flow of liquids. This may make it difficult for the solder paste to flow or create difficulty in forming a stable coating on the surface.

[0188] In order to form the surface roughness within the above range, the shape of the metal column and the soft etching and electroplating conditions may be appropriately adjusted.

[0189] The solder joint is the part where the solder paste on the first side surface reflows and hardens on the first connection surface and the second connection surface at both ends of the connection column to form a physical and electrical connection. In this solder joint, the flux component of the solder paste completely disappears, so only the solder powder part remains after melting and reflowing. At this time, the melting rate of the solder powder is more than 99%.

[0190] After the solder paste is reflowed, voids will be generated in the solder joints. The number of these voids may vary depending on the amount of solder paste applied and the thickness of the coating. If the coating is too thick, the coating may flow, resulting in voids in the solder joints. In the present invention, the voids formed in the solder joints are preferably no more than 10%.

[0191] Such semiconductor packages can be made into various structures as follows.

[0192] The first embodiment of semiconductor packaging is shown in FIG. Figure 3 According to this, the semiconductor package includes a first connection body providing a first connection surface, a solder joint, a first connection column, a semiconductor chip, and a second connection body.

[0193] The first connector is a lower substrate, and the second substrate is an upper substrate. The first connecting column electrically connects the first substrate and the second substrate, and has a columnar outer shape and is provided with a solder column of a solder layer. The solder joint connects the first connecting surface of the first connector and the first end of the connecting column.

[0194] The semiconductor chip is arranged on the first surface of the first connecting body, a solder bump (solder bump) is arranged on the bottom surface of the semiconductor chip, and a filler is arranged between the semiconductor chip and the first connecting body.

[0195] The second embodiment of the semiconductor package is shown in FIG. Figure 4The difference between the second embodiment and the first embodiment is that the connection pillars used in the second embodiment are metal pillars without a solder layer.

[0196] The third embodiment of the semiconductor package is shown in FIG. Figure 5 In the third embodiment, a solder column with a solder layer is used as a connecting column, and there is no solder joint, and only a solder flux is provided around the first end of the connecting column and the first connecting surface. In this embodiment, the thickness of the solder layer is preferably 5 to 8 μm.

[0197] The fourth embodiment of the semiconductor package is shown in FIG. Figure 6 In the first to third embodiments described above, the first connection body and the second connection body are the lower substrate and the upper substrate, respectively. However, in the fourth embodiment, the first connection body is the lower substrate, and the second connection body is a semiconductor chip.

[0198] The fifth embodiment of the semiconductor package is shown in FIG. Figure 7 The fifth embodiment differs from the other embodiments in that it includes two or more stacked semiconductor chips.

[0199] Next, a method of manufacturing a semiconductor package will be described.

[0200] The method for manufacturing a semiconductor package includes a step of providing a first connection surface, a step of connecting a first end portion, a step of attaching a semiconductor chip, a molding step, a step of providing a second connection surface, and a step of connecting a second end portion.

[0201] The step of providing the first connection surface is a step of providing a first connection body having a first connection surface.

[0202] According to various structural forms of semiconductor packaging, the first connection surface can be a PCB, an interposer, an RDL, and an electrical first connection surface such as an electrode, a pad, a terminal, a wiring, a bump, etc. arranged on a flexible substrate. At this time, solder paste or flux can be provided on the first connection surface connected to the first end of the connecting column.

[0203] The first end connection step is a step of connecting the first end of the connection column to the first connection surface. In this step, the solder layer formed on the connection column or the solder paste or flux provided on the first connection surface is solidified after reflow soldering to form a solder joint, and the first end is attached to the first connection surface.

[0204] The semiconductor chip attaching step is a step of attaching the semiconductor chip to the first connecting body. In this step, the semiconductor chip can be attached to the first side with the terminals or the second side opposite thereto.

[0205] The molding step is a step of filling the semiconductor chip with resin to protect it. In this process, the connection column should be exposed from the upper surface of the mold to make electrical connection.

[0206] The second connection surface providing step is a step of providing a second connection body opposite to the first connection body. Similar to the first connection surface providing step, according to various structural forms of semiconductor packaging, the second connection surface can be an electrical connection surface such as an electrode, pad, terminal, wiring, bump, etc. provided on a connection body such as a PCB, an interposer, an RDL, a flexible substrate, a film, etc. At this time, solder paste or flux can be provided on the second connection surface connected to the second end of the connection column.

[0207] The second end connection step is a step of connecting the second end of the connection column to the second connection surface. In this step, the solder layer formed on the connection column or the solder paste or flux provided on the second connection surface is solidified after reflow soldering to form a solder joint, and the second end is attached to the second connection surface.

[0208] Figure 8 A manufacturing method is described in which, in a semiconductor chip attaching step, a first surface of a terminal formed on a semiconductor chip is bonded to a first connection surface, and a manufacturing method in which a surface opposite to the terminal is bonded to the first connection surface.

[0209] <Examples 1 to 7> Solder Paste

[0210] The D50 diameter is 3.23.2μm, the content of solder powder less than 1μm is 7wt% of the total content of solder powder, the content of solder powder greater than 8μm is 0.3wt%, and 87.5g of SAC305 solder powder with an oxygen content of 710ppm and 12.5g of flux are mixed. At this time, the composition of the flux is: Tetrakisethylenediamine 35wt%, 2-Iodobenzoicacid 0.5wt%, Succinic acid 3wt%, Propylene Glycol Ether 35wt% and α-terpineol 6.5wt%.

[0211] Solder pastes of Examples 2 to 7 were prepared in the same manner as in Example 1, and their compositions are shown in Tables 1 and 2.

[0212] Table 1

[0213]

[0214]

[0215] Table 2

[0216]

[0217]

[0218] <Comparative Example>: Solder Paste

[0219] Solder pastes of Comparative Examples 1 to 7 were prepared in the same manner as in Example 1, and their compositions are shown in Tables 3 and 4.

[0220] Table 3

[0221]

[0222] Table 4

[0223]

[0224] <Example 8 to Example 10><Comparative Example 5 to Comparative Example 11>: Solder Column

[0225] The entire surface of the metal column is coated with a solder layer composed of Sn-Ag-Cu. First, the copper alloy column is pickled, then the copper alloy column is placed in a barrel, Sn-Ag is hung on the anode, and then MS-Cu plating solution and additives are added to the plating solution, and the cathode is hung on the copper alloy column for electrolytic plating.

[0226] During this process, the temperature needs to be maintained at 2030°C. Electrolytic plating is performed at a current density of 1A / dm from 30 minutes to 3 hours to form a first solder layer with a thickness of about 16μm. In this way, solder pillars with materials of different sizes, roughness, and edge R values ​​are manufactured and summarized in Table 5.

[0227] Table 5

[0228]

[0229]

[0230] <Example 11> Metal Pillar

[0231] Copper alloy wires were prepared by mixing Sn with molten copper to a concentration of 5.0%. Next, these copper alloy wires were drawn through a die so that the diameters of the top and bottom surfaces were The copper alloy wire is cut at positions where the length (height L) is 120 μm, and then the copper alloy wire is cut at positions where the length (height L) is 180 μm and 300 μm, thereby manufacturing the desired copper alloy column. The cutting is performed by a die cutting method.

[0232] Next, the copper alloy column was annealed. The annealing conditions were: the heating time from room temperature to 200°C was 20 minutes, the time of maintaining at 200°C was 180 minutes, and the time of cooling from 200°C to room temperature was 20 minutes. The furnace was cooled using a cooling fan installed in the furnace.

[0233] <Experimental Example 1> Viscosity, Thixotropy, Tackiness

[0234] The viscosity and tackiness of Examples 1 to 7 and Comparative Examples 1 to 7 of the solder paste were measured and summarized in Tables 6, 7, and 8.

[0235] The viscosity and thixotropy were measured using a rheometer.

[0236] When measuring viscosity, the value at 10 RPM is used, and the value of thixotropy between 3 RPM and 30 RPM is taken as the logarithm. (Thixotropy = log (3 rpm / 30 rpm))

[0237] Tackiness is measured using Malcom's Tackiness tester (TK-1), which measures the force when a probe in the center of the printed solder paste touches it and falls off. If the rate of change after 4 hours exceeds 30%, it is considered that the product may have deteriorated.

[0238] Table 6

[0239]

[0240] Table 7

[0241]

[0242]

[0243] Table 8

[0244]

[0245] <Experimental Example 2> Weldability

[0246] Weldability was evaluated based on the internal limit sample, and the weld shape after melting was observed under a microscope, and a score of 1 to 5 was given. Examples 1 to 7 and Comparative Examples 1 to 7 were evaluated according to the following criteria: (1 point is no melting at all, 2 points is that the melting characteristics of the powder are insufficient, 3 points is melted but cold welding occurs in some places, 4 points is good melting but the surface roughness is slightly rough, and 5 points is complete melting and excellent surface condition). In order to make the scoring objective, Fig.21 Standardized images are provided. The weldability results are summarized in Tables 9, 10, and 11.

[0247] Table 9

[0248]

[0249] Table 10

[0250]

[0251] Table 11

[0252]

[0253] In addition, Fig.23 The photographs of the corresponding results are collated in . According to these, the weldability of Examples 1 to 7 is poor, and the weldability of Comparative Examples 1 to 7 is also poor.

[0254] <Experimental Example 3> Measurement of Tilting Degree and Missing Rate

[0255] On a PCB with an area of ​​50mm*40mm covered with a Cu pad with a thickness of 18μm, a connecting column with a diameter of 120μm, a length of 300μm, an aspect ratio of 2.5, and a solder layer thickness of 1μm was used. After welding the electrodes and the connecting column, the solder paste of Examples 1 to 7 and Comparative Examples 1 to 5 was reflowed and then hardened, and the Tilting degree and Missing rate of the connecting column were measured.

[0256] Tilting degree Fig. 9 As shown in Figure 1, the angle difference between the center point of the connection column randomly attached to the connection surface and the connection surface connecting line and the connection surface perpendicular line is measured, and its maximum value is expressed. Missing is the ratio of connection column shedding measured before and after the reflow process, and is expressed as a percentage. These results have been sorted out in Tables 12 and 13.

[0257] Table 12

[0258]

[0259]

[0260] Table 13

[0261]

[0262] on the other hand, Fig.10 The photographs showing the degree of Tilting and Missing of Example 3 and Comparative Example 3 are shown.

[0263] <Experimental Example 4>: Solder Powder Particle Size Distribution

[0264] Fig.11 and Fig.12This is a graph showing the particle size distribution of the solder powder used in Example 3 and Comparative Example 3. According to this, D50 of Example 3 is 3.227, particles of 1 μm or less account for 6.99%, and particles of 8 μm or more account for less than 0.3%.

[0265] <Experimental Example 4>: Electron Microscope Photograph

[0266] After the connection column was connected to the connection surface using the solder paste of Example 3 of the present invention and Comparative Example 3, an electron microscope was used to take pictures. Fig.13 In addition, 3-point measurements were performed to measure the thickness of the solder joint between the connection column and the connection surface, and Fig.14 It can be seen that the thickness of the solder joint between the connection column and the connection surface is consistent.

[0267] <Experimental Example 5>: Tilting degree, voids, missing rate and wetting properties

[0268] The degree of Tilting, voiding, missing rate, and Wetting property of Examples 8 to 9 and Comparative Examples 5 to 11 were measured and summarized in Table 14. At this time, the paste of Example 5 was used as the solder paste.

[0269] Table 14

[0270]

[0271]

[0272] Fig. 20 The photographs show the difference in tilt angle and missing rate between Example 10 and Comparative Example 11 according to the edge R value. Fig.21 This is a photograph of a defect inspection in Comparative Example 8, in which no electroplating layer is formed on the outer surface of the metal needle. Fig. 22 This photo shows the evaluation criteria used to determine the weldability evaluation criteria during internal evaluation.

[0273] The features, structures, effects, etc. shown in the aforementioned embodiments may be combined or modified to implement other embodiments for those with common knowledge in the field of the embodiments. Therefore, the contents of these combinations and modifications should be interpreted as being included in the scope of the present invention.

Claims

1. A solder paste for connecting columns, comprising: Solder powder, wherein the mean value of the particle size of the powder containing tin is 3 to 5 μm, and the proportion of the powder with a particle size of 8 μm or more is less than 1% by weight; and The soldering flux is used to improve the wettability of the solder powder.

2. The solder paste for connecting column according to claim 1, The proportion of the powder having a particle size of less than 1 μm is less than 10% by weight.

3. The solder paste for connecting column according to claim 1, The oxygen concentration of the powder is 800 ppm or less.

4. The solder paste for connecting column according to claim 1, The content of the soldering flux in the total weight of the solder paste is 10 to 20 weight %.

5. The solder paste for connecting column according to claim 1, The soldering flux comprises a solvent, a surfactant, an activator, an amine-based activator and additives.

6. The solder paste for connecting column according to claim 5, The amine-based activator includes at least one selected from the group consisting of triethanolamine, diethanolamine, tetraethylenediamine, and polyoxyethylene tallow amine.

7. The solder paste for connecting column according to claim 6, The amine-based activator may be included in an amount of 120 to 150 parts by weight relative to 100 parts by weight of the solvent.

8. The solder paste for connecting column according to claim 5, The activating agent comprises an organic acid, namely a first activating agent, and a halogen compound, namely a second activating agent.

9. The solder paste for connecting column according to claim 8, The halogen compound is a bromine compound.

10. The solder paste for connecting column according to claim 9, The bromine compounds are cetyltrimethylammonium bromide and trans-2,3-dibromo-2-butene-1,4-diol.

11. The solder paste for connecting column according to claim 9, The halogen compound is an iodine compound.

12. The solder paste for connecting column according to claim 11, The iodine compounds are 2-iodobenzoic acid and 3,5-diiodosalicylic acid.

13. The solder paste for connecting column according to claim 1, The flux also contains additional de-fluxing agent for preventing residual, The de-soldering flux includes at least one substance selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, butyl carbitol, hexyl carbitol, and diethylene glycol diethyl ether.

14. The solder paste for connecting column according to claim 1, The CV value of the solder powder is 40 to 50%.

15. The solder paste for connecting column according to claim 14, The surfactant is one selected from the group consisting of propylene glycol ether, ethylene glycol ether, diethylene glycol ether, triethylene glycol ether and glycol ether acetate.

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