TWI801734B - Solder alloys, solder powders, solder pastes, solder balls and solder preforms - Google Patents

Abstract

The present invention provides a solder alloy capable of suppressing Fe corrosion in a solder bath, improving the mechanical strength of a solder joint, and preventing short circuits, solder powder, solder paste, solder ball, solder preform, and solder joint using the solder alloy. The solder alloy system has an alloy composition of Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, and the rest is Sn in mass %.

Description

Solder alloys, solder powders, solder pastes, solder balls and solder preforms

The present invention relates to a solder alloy, solder powder, solder paste, solder ball and solder preform capable of suppressing Fe corrosion.

Mounting boards in which electronic components are mounted on printed boards are used in various electronic devices. As the mounting substrate, in addition to a single-layer substrate, a plurality of substrates laminated in order to realize sufficient functions may be used. Conduction between substrates and mounting of electronic components on substrates include a method of connecting by surface mounting or a method of mounting by inserting terminals into through holes of the substrate. As such a mounting process to a printed circuit board, flow soldering, reflow soldering, manual soldering, etc. are mentioned.

Among them, when mounting an electronic component having a certain size, a method of mounting a terminal by inserting it into a through hole is used from the viewpoint of connection strength or the like. Flow soldering is usually used as the mounting step. Flow soldering is a method of soldering by aligning the spray surface of the solder bath with the connection surface side of the printed circuit board.

In flow soldering, a solder bath is required. Since there is high temperature molten solder flowing in the solder bath for a long time, the corrosion resistance For the solder bath, use stainless steel whose main component is Fe. However, due to long-term use, the inner surface of the solder bath is corroded by Fe corrosion. The reason for such Fe corrosion is considered to be that Sn and Fe in the solder alloy are alloyed by interdiffusion, and this is Sn that is easily dissolved in molten solder. Since re-examination of the material of the solder bath is costly and time-consuming, it is necessary to review the solder alloy that can suppress the corrosion of Fe.

Patent Document 1 discloses a solder alloy containing predetermined amounts of Fe and Ge in order to suppress Fe corrosion.

[Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2008-168322

The invention described in Patent Document 1 is not limited to prolonging the life of the solder bath, but also aims at suppressing Fe corrosion of Fe plating applied to the soldering iron tip of a soldering iron, etc., and suppressing it under severe environments where Fe corrosion is likely to occur. Fe attack. In this way, in the invention described in the same document, since the focus is only on suppressing the corrosion of Fe in any environment, a solder alloy containing a large amount of Fe and also containing Ge has been disclosed.

However, when a large amount of Fe is contained in a solder alloy mainly composed of Sn, needle-like crystals derived from the SnFe compound are precipitated, and there is a possibility of a short circuit. Also, the solder alloy described in Patent Document 1 is for A large amount of Ni may be contained to improve wettability. When the Ni content is high, the SnCuNi compound is precipitated near the joint interface of the solder alloy, which may lower the mechanical strength of the solder joint.

In this way, the conventional solder alloys were designed focusing only on the corrosion of Fe, and the mechanical strength required from the beginning as a solder joint had to be ensured even in the conventional solder alloys. Therefore, in addition to Fe corrosion, it is necessary to design the alloy in such a way that the mechanical strength of the solder joint which is the most important part of the solder alloy can be ensured.

The object of the present invention is to provide a solder alloy that can suppress Fe corrosion in a solder bath, improve the mechanical strength of a solder joint, and prevent short circuits, and solder powder, solder paste, solder balls, and solder preforms using the solder alloy.

The inventors of the present invention focused on Fe corrosion in the solder bath and suppressed the precipitation of needle crystals, and therefore examined in detail the composition of an alloy containing Ge in a solder alloy with a low Fe content. Furthermore, in order to improve the mechanical strength of the solder joint, the present inventors focused on not precipitating the SnCuNi compound in the vicinity of the joint interface of the solder alloy, and further examined an alloy composition for suppressing the Ni content. In addition, in order to improve the mechanical strength of the solder joint, the present inventors also focused on preventing intermetallic compounds such as Cu ₃ Sn or Cu ₆ Sn ₅ from growing on the joint interface between the electrode and the solder alloy. Therefore, detailed examination was performed on an alloy composition containing a predetermined amount of Cu with a low Fe content and a Ni content.

As a result, it was found by accident that the Fe corrosion of the solder bath can be sufficiently suppressed in a range where the Fe content is less than that of conventional solder alloys. It was also found that the precipitation of needle crystals can be suppressed because the Fe content is small. In addition, it was found that the precipitation of the SnCuNi compound can be suppressed in the vicinity of the joint interface of the solder alloy due to the low Ni content. In addition, it is also found that if the content of Fe or Ni is too small, intermetallic compounds such as Cu ₃ Sn or Cu ₆ Sn ₅ grow, so a certain amount of these elements must be contained.

Also, as a preferable aspect, it has been found that when at least one set of Ni and Fe, Cu and Ni, Cu and Fe, and Ge and Fe satisfies the respective predetermined relationships, the above-mentioned effects can be exhibited more sufficiently. As another preferred aspect, the following insights were obtained: Furthermore, the solder alloy containing As can exert the thickening suppression effect of the solder paste and suppress yellowing of the solder paste by concentrating As on the surface of the solder alloy, and can also maintain the solder. alloy wettability.

The present invention based on these findings is as follows.

(1) A solder alloy characterized by: Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, and the rest being Sn in mass%. alloy composition.

(2) The solder alloy as described in said (1) whose alloy composition further contains Ag: 0-4.0% by mass %.

(3) The solder alloy according to the above (1) or the above (2), wherein the alloy composition further satisfies the following formulas (1) to (5).

0.0430%≦Ni+Fe≦0.0700% (1)

3.50≦Ni/Fe≦30.00 (2)

10.83≦Cu/Ni≦18.57 (3)

65.00≦Cu/Fe≦325.00 (4)

0.0060%≦Ge+Fe≦0.0280% (5)

In the formulas (1) to (5) above, Ni, Fe, Cu, and Ge represent the contents (% by mass) of the respective alloy compositions.

(4) The solder alloy according to any one of the above (1) to the above (3), wherein the alloy composition further contains As in mass %: 0.0040 to 0.0250%.

(5) A solder paste comprising solder powder and flux consisting of the solder alloy according to any one of the above (1) to the above (4).

(6) A solder ball made of the solder alloy described in any one of the above (1) to the above (4).

(7) A solder preform made of the solder alloy described in any one of the above (1) to the above (4).

[Fig. 1] is a graph of XPS analysis of the solder ball surface.

[Fig. 2] is a graph of XPS analysis of the solder ball surface.

[Fig. 3] is a graph of XPS analysis of the solder ball surface.

The present invention is explained in detail by the following. In this manual, The "%" of the solder alloy composition is "mass%" unless otherwise specified.

1. Alloy composition (1) Cu: 0.55~0.75%

Cu is an element that is used in general solder alloys and improves the bonding strength of solder joints. In addition, Cu is an element more expensive than Sn, and by coexisting with As, Cu promotes the thickening suppression effect of As. When Cu is less than 0.55%, the strength of the solder joint cannot be improved. The lower limit of the Cu content is more than 0.55%, preferably more than 0.55%, more preferably more than 0.60%. On the other hand, if the Cu content exceeds 0.75%, the melting point of the solder alloy will rise, causing thermal damage to electronic components. The upper limit of the Cu content is 0.75% or less, preferably less than 0.75%, more preferably 0.70% or less.

(2) Ni: 0.0350~0.0600%

Ni-based, an element that inhibits the growth of intermetallic compounds such as Cu ₃ Sn or Cu ₆ Sn ₅ at the joint interface. When the Ni content is less than 0.0350%, these intermetallic compounds grow and the mechanical strength of the solder joint deteriorates. The lower limit of the Ni content is 0.0350% or more, preferably more than 0.0350%, more preferably 0.0400% or more. On the other hand, if the Ni content exceeds 0.0600%, a large amount of SnCuNi compound is precipitated near the joint interface in the solder alloy, and the mechanical strength of the solder joint deteriorates. The upper limit of the Ni content is 0.0600% or less, preferably less than 0.0600%, more preferably 0.0550% or less.

(3) Ge: 0.0035~0.0200%

Ge is an element that suppresses oxidation of the solder alloy to prevent discoloration or deterioration of wettability of the solder alloy, and is an element that suppresses generation of dross derived from Fe. When the Ge content is less than 0.0035%, discoloration of the solder alloy or deterioration of wettability occurs. The lower limit of the Ge content is above 0.0035%, preferably above 0.0040%, more preferably above 0.0080%. On the other hand, when the Ge content exceeds 0.0200%, wettability deteriorates due to precipitation of a large amount of oxides on the surface of the solder alloy, and the mechanical strength of the solder joint deteriorates accordingly. The upper limit of the Ge content is 0.0200% or less, preferably less than 0.0200%, more preferably 0.0150% or less, most preferably 0.0120% or less.

(4) Fe: 0.0020~0.0100%

Fe-based, when the solder alloy is melted in a solder bath made of iron or stainless steel, it inhibits the corrosion of Fe on the inner surface of the solder bath, and inhibits the growth of intermetallic compounds such as Cu ₃ Sn or Cu ₆ Sn ₅ at the joint interface similarly to Ni of elements. Also, within the above range, the precipitation of needle crystals due to the SnFe compound can be suppressed, and a circuit short circuit can be prevented. The so-called needle-shaped crystals in the present invention means that in a SnFe compound, the aspect ratio of the ratio of the major axis to the minor axis is 2 when observed in the range of 300 μm × 300 μm in the cross-sectional SEM photograph of the solder alloy. above crystallization.

If the Fe content is less than 0.0020%, Fe corrosion of the solder bath occurs, and coarse Cu ₆ Sn ₅ compounds are precipitated. The lower limit of the Fe content is at least 0.0020%, preferably at least 0.0050%. On the other hand, if the Fe content exceeds 0.0100%, needle-shaped crystals will be precipitated and the circuit will be short-circuited. The upper limit of the Fe content is 0.0100% or less, preferably less than 0.0100%, more preferably 0.0080% or less.

(5) Ag: 0~4.0%

Ag is an arbitrary element that can form Ag ₃ Sn at the crystal interface to improve the reliability of the solder alloy. In addition, Ag is an element more expensive than Sn, and the thickening suppression effect of As is promoted by coexisting with As. Furthermore, if the Ag content is within the above range, since the rise of the melting point can be suppressed, Fe corrosion can also be suppressed without excessively raising the preset temperature in the solder bath. The Ag content is preferably 0-4%, more preferably 0.5-3.5%, even more preferably 1.0-3.0%, particularly preferably 2.0-3.0%.

(6) At least one of the formulas (1)~(5)

0.0430%≦Ni+Fe≦0.0700% (1)

3.50≦Ni/Fe≦30.00 (2)

10.83≦Cu/Ni≦18.57 (3)

65.00≦Cu/Fe≦325.00 (4)

0.0060%≦Ge+Fe≦0.0280% (5)

In the formulas (1) to (5) above, Ni, Fe, Cu, and Ge represent the contents (% by mass) of the respective alloy compositions.

In addition to the content of each constituent element in the solder alloy system of the present invention within the above-mentioned range, at least two kinds of Ni, Fe, Cu, and Ge preferably satisfy at least one of the above-mentioned formulas (1)-(5). Each constituent element of the solder alloy does not act independently, but all the contents of each constituent element In the case of a certain range, various effects can start to be exerted. In the present invention, in addition to the content of each constituent element being within the above range, Fe and Ni, Fe or Ni and other elements that are related to the suppression of Fe corrosion, the improvement of the mechanical strength of the solder joint, and the suppression of circuit short circuits satisfy each other. Given the relationship, the effects of the present invention can be brought into full play.

It is preferable to satisfy at least one of formula (1) and formula (2), formula (3), formula (4) and formula (5), and it is more preferable to satisfy formula (1)~(5) at the same time.

Also, Ni and Fe system, formula (1) is preferably 0.0430%~0.0700%, more preferably 0.045%~0.0600%; formula (2) is preferably 3.50~30.00, more preferably 6.25~30.00. Cu and Ni system, formula (3) is preferably 10.83~18.57, more preferably 11.0~15.0. Cu and Fe system, formula (4) is preferably 65.00~325.00, more preferably 81.25~325.00. Ge and Fe system, formula (5) is preferably 0.0060%~0.0280%, more preferably 0.0100%~0.0200%.

(7) As: 0.0040~0.0250%

As is an optional element that suppresses yellowing in order to form an As-concentrated layer on the surface of the solder alloy. In addition, when the solder alloy of the present invention is added as solder powder to the solder paste, the thickening suppressing effect is exerted. The lower limit of the As content is to fully exhibit the effect of containing As, and it is preferably 0.0040% or more, more preferably more than 0.0040%. On the other hand, wettability can be maintained when As is 0.0250% or less. The upper limit of the As content is preferably at most 0.0250%, more preferably at most 0.0200%, even more preferably at most 0.0100%.

In the present invention, the As concentration layer formed when the so-called As is contained means that the As concentration is higher than the average As concentration in the solder material (the mass phase of As). Specifically, the presence of the region of the mass ratio of the solder alloy can be confirmed by the criteria for determination described later. The As-concentrated layer preferably exists on at least a part of the surface side of the solder alloy, and more preferably covers the entire surface.

The reason why yellowing can be suppressed and the temporal change in solder paste viscosity can be suppressed when an As-concentrated layer is formed when As is contained as in the present invention is not clear, but it is presumed as follows. The increase in viscosity is considered to be caused by the formation of salt due to the reaction between Sn or Sn oxide and various additives such as activators contained in the solder paste (flux), or agglomeration of solder powder. It is speculated that if an As-concentrated layer exists on the surface like the solder alloy of the present invention, the As-concentrated layer will be interposed between the solder powder and the flux, and the above-mentioned reaction will not easily occur, so the above-mentioned effects will be exhibited at the same time.

(7-1) Judgment criteria for As-concentrated layer

In a sample with a size of 5.0mm×5.0mm (when the solder material is not in the form of a plate, the solder material (solder powder, solder ball, etc.) is spread to the range of 5.0mm×5.0mm without gaps) , select any area of 700 μm×300 μm, and perform XPS analysis with ion sputtering. One region is selected for each sample, and each of the three samples is analyzed once for a total of three times. In the case of S1≧S2 in all three analyzes, it was judged that an As-concentrated layer was formed.

Here, the definitions of S1, S2, and D1 are as follows.

S1: In the graph of the XPS analysis performed on the above sample, the integrated value of the detection intensity of As in the region where the depth converted to SiO ₂ is 0~2×D1(nm)

S2: In the XPS analysis chart, the integrated value of the detection intensity of As in the region where the depth converted to SiO ₂ is 2×D1~4×D1 (nm)

D1: In the graph of XPS analysis, the detection intensity of O atoms becomes the maximum detection intensity (Do.max) in the part deeper than the depth (Do.max (nm)) converted to SiO ₂ at which the detection intensity of O atoms becomes the maximum The depth (nm) of the initial SiO ₂ conversion of 1/2 the intensity at which the intensity is located.

The detailed conditions of the criteria for determining the above-mentioned As-concentrated layer follow the descriptions in the examples. Like the solder alloy of the present invention, by having an As-concentrated layer on the surface, yellowing of the solder alloy can be suppressed and an increase in the viscosity of the solder paste can be suppressed.

(7-2) Thickness of As Concentrated Layer

The thickness of the As concentrated layer (in terms of SiO ₂ ) is preferably from 0.5 to 8.0 nm, more preferably from 0.5 to 4.0 nm, most preferably from 0.5 to 2.0 nm. When the thickness of the As concentration layer is within the above range, yellowing is suppressed and a solder material having excellent wettability can be obtained.

(7-3) Yellowness

In the present invention, the yellowness b* in the L*a*b* color system of the solder alloy is preferably 0-10.0, more preferably 3.0-5.7, most preferably 3.0-5.0. If the yellowness b* in the L*a*b* color system of the solder material is within the above range, the yellowness is low. Since the solder has a metallic luster, it can be reliably detected in the automatic processing of the image recognition of the solder joint. out solder joints.

Among the present invention, the yellowness b* system uses the CM-3500d2600d type spectrophotometer (manufactured by Konica Minolta Corporation), at D65 light source, 10 degrees In the field of view, the spectral transmittance was measured in accordance with JIS Z 8722:2009 "Measurement method of color - reflected and transmitted object color", and obtained from the color value (L*, a*, b*).

(8) Rest: Sn

The remainder of the solder alloy of the present invention is Sn. In addition to the aforementioned elements, unavoidable impurities may also be contained. Even in the case of containing unavoidable impurities, it will not affect the aforementioned effects.

2. Solder powder

The solder powder of the present invention is used in the solder paste described later, and is preferably spherical powder. By being a spherical powder, the fluidity of the solder alloy is improved. When the solder powder of the present invention is a spherical powder, it is preferable to satisfy the size (particle size distribution) of 1 to 8 in the powder size classification (Table 2) of JIS Z 3284-1:2014. It is more preferable to satisfy the size (particle size distribution) of 4~8, and more preferably to satisfy the size (particle size distribution) of 5~8. If the particle size satisfies this condition, the surface area of the powder will not be too large and the increase in viscosity can be suppressed, and the aggregation of fine powder can be suppressed to suppress the increase in viscosity. Therefore, welding of finer parts becomes possible.

The true sphericity of the solder powder is preferably at least 0.90, more preferably at least 0.95, most preferably at least 0.99. In the present invention, the true sphericity of the spherical powder is measured using a CNC image measuring system (ULTRA Quick Vision ULTRA QV350-PRO measuring device manufactured by MITUTOYO Co., Ltd.) using the minimum zone center method (MZC method). In the present invention, the so-called true sphericity It means the deviation from the true ball. For example, it is the arithmetic mean calculated by dividing the diameter of 500 balls by the major diameter. The closer the value is to the upper limit of 1.00, the closer to the true ball.

3. Solder paste

The solder paste of the present invention contains the aforementioned solder powder and flux.

(1) Components of flux

Flux used in solder paste is organic acid, amine, amine hydrogen halide, organic halogen compound, thixotropic agent, rosin, solvent, surfactant, base agent, polymer compound, silane coupling agent, colorant Either one, or a combination of two or more.

Examples of organic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, and 2,2-bismethylolpropionic acid , tartaric acid, malic acid, glycolic acid, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, oleic acid, etc.

Examples of the amine include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2 -Dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl- 2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1 -Cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2 ,4-Diamino-6-[2 ' -methylimidazolyl-(1 ' )]-ethyl-s-triazine, 2,4-diamino-6-[2 ' -undecyl Imidazolyl-(1 ' )]-ethyl-s-triazine, 2,4-diamino-6-[2 ' -ethyl-4 ' -methylimidazolyl-(1 ' )]-ethyl -s-triazine, 2,4-diamino-6-[2 ' -methylimidazolyl-(1 ' )]-ethyl-s-triazine isocyanuric acid adduct, 2-benzene Imidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro- 1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-Diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamine Base-6-methacryloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-Ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2-( 2' -hydroxy-5' - methyl phenyl)benzotriazole, 2-( 2' -hydroxy-3' - tert-butyl- 5' -methylphenyl)-5-chlorobenzotriazole, 2-( 2' -hydroxy- 3 ' , 5' -di-tert-pentylphenyl)benzotriazole, 2-( 2' -hydroxy- 5' -tert-octylphenyl)benzotriazole, 2,2' -methylene Bis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6' - tert -Butyl- 4' -methyl- 2,2' -methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl base]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2 ' -[[(methyl -1H-Benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1 ' , 2' -dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxy Propyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]- 4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of amines include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, xylylguanidine, methylimidazole, 2 -Ethyl-4-methylimidazole, etc. Examples of the hydrogen halide include hydrides of chlorine, bromine, and iodine.

Examples of organohalogen compounds include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate 6 bromide, 1-bromo-2-butanol , 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2- Propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, etc.

Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. As a wax-type thixotropic agent, hydrogenated castor oil etc. are mentioned, for example. Examples of the amide-based thixotropic agent include monoamide-based thixotropic agents, bisamide-based thixotropic agents, and polyamide-based thixotropic agents. Specifically, lauric acid amide, palmitic acid amide, Stearic acid amides, behenic acid amides, hydroxystearic acid amides, saturated fatty acid amides, oleic acid amides, erucamides, unsaturated fatty acid amides, p-toluamide, aromatic amides Amine, Methylenebisstearamide, Ethylbislaurateamide, Ethylbishydroxystearamide, Saturated Fatty Acid Bisamide, Methylenebisoleamide, Unsaturated Fatty Acid Bisamide, m-xylene bisstearamide, aromatic bisamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, hydroxymethyl stearic acid Amide, hydroxymethylamide, fatty acid ester amide, etc. Examples of the sorbitol-based thixotropic agent include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, and the like.

Examples of the base include nonionic surfactants, weak cationic surfactants, rosin, and the like.

Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyol polyoxyethylene Additions etc.

Examples of weak cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adducts, and aromatic amine polyoxyethylene adducts , Polyamine polyoxyethylene adduct.

Examples of the rosin include raw material rosins such as rosin gum, wood rosin, and tall oil rosin, and derivatives obtained from the raw material rosins. Examples of such derivatives include purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, and modified α, β unsaturated carboxylic acids (acrylated rosin, maleated rosin, fumarated rosin etc.), and the refined product, hydrogenated product, and disproportionated product of the polymerized rosin, and the refined product, hydrogenated product, and disproportionated product of the α, β unsaturated carboxylic acid modified product, etc., and two or more types may be used. Also, in addition to rosin-based resins, it may further contain terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, and modified terpene resins. At least one or more resins of high-quality xylene resins. As the modified terpene resin, an aromatic modified terpene resin, a hydrogenated terpene resin, a hydrogenated aromatic modified terpene resin, or the like can be used. As the modified terpene phenol resin, a hydrogenated terpene phenol resin or the like can be used. As the modified styrene resin, styrene acrylic resin, styrene cis Butenedioic acid resin, etc. Examples of modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, polyoxyethylene-added di Toluene resin, etc.

Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, terpineols, and the like. Examples of alcohol-based solvents include isopropanol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl- 1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl- 2,3-butanediol, 1,1,1-para(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2' -oxybis( Methyl)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2 ,2-(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threose alcohol, guaiacol glyceryl ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7- diol, etc. Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, etc.

Examples of the surfactant include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, Polyoxyalkylene alkylamide, etc.

(2) Flux content

Relative to the total mass of the solder paste, the flux content is preferably 5-95%, More preferably 5~15%. Within this range, the effect of suppressing thickening due to the solder powder can be sufficiently exhibited.

(3) Manufacturing method of solder paste

The solder paste of the present invention is manufactured by a general method in the industry. First, known methods such as a drop method of dropping molten solder material to obtain particles, a spray method of centrifugal spraying, and a method of pulverizing bulk solder material can be used to produce solder powder. In the dropping method or the spraying method, in order to form particles, the dropping or spraying is preferably performed in an inert environment or in a solvent. Then, the above-mentioned components can be heated and mixed to prepare a flux, and the above-mentioned solder powder or zirconia powder as the case may be introduced into the flux, stirred and mixed to manufacture.

4. Solder balls

The solder alloy of the present invention can be used as a solder ball. When used as solder balls, solder balls can be produced by using the solder alloy of the present invention by the drop method which is a common method in the industry. Furthermore, solder joints can be produced by processing the solder balls by a method generally used in the industry, such as mounting and bonding one solder ball on one electrode coated with flux. The lower limit of the particle size of the solder balls is preferably at least 1 μm, more preferably at least 10 μm, still more preferably at least 20 μm, particularly preferably at least 30 μm. Also, the upper limit of the particle size of the solder balls is preferably at most 3000 μm, more preferably at most 1000 μm, still more preferably at most 600 μm, particularly preferably at most 300 μm.

5. Solder preform

The solder alloy of the present invention can be used as a preform. Examples of the shape of the preform include a gasket, ring, pellet, disk, ribbon, wire, and the like.

6. Solder joints

The solder alloy of the present invention can join the electrodes of PKG (Package) such as IC chips and the electrodes of substrates such as PCB (printed circuit board) to form solder joints. The solder joint is composed of electrodes and solder joints. The term "solder joint" mainly refers to a portion formed of a solder alloy.

7. Formation method of solder alloy

The method for producing the solder alloy of the present invention is not limited, and it can be produced by melting and mixing raw material metals.

When the solder alloy contains As, the method of forming the As-concentrated layer is also not limited. As an example of the formation method of an As concentrating layer, heating a solder material in an oxidizing atmosphere (air or an oxygen atmosphere) is mentioned. Although heating temperature is not limited, For example, it may be 40-200 degreeC, and may be 50-80 degreeC. The heating time is also not limited, for example, it may be several minutes to several days, preferably several minutes to several hours. In order to form a sufficient amount of As concentrating layer, the heating time is preferably 10 minutes or more, more preferably 20 minutes or more.

The solder alloy system of the present invention can produce a low α wire alloy by using a low α wire material as its raw material. Such a low alpha alloy, if used to form solder bumps around the memory, can suppress soft errors.

[Example]

The present invention is illustrated by the following examples, but the present invention is not limited to the following examples.

Using the solder alloys (mass %) described in Examples and Comparative Examples in Tables 1 to 5, evaluations were made on 1. Inhibition of elution of Fe in a solder bath, 2. Inhibition of precipitation of acicular crystals, and 3. IMC with respect to Cu Growth inhibition, 4. SnCuNi formation inhibition in the bump. In addition, for the examples and comparative examples containing As in Tables 3 to 5, 5. surface concentration of As, 6. inhibition of thickening, 7. change in yellowness, and 8. solder wettability were further evaluated together.

1. Inhibition of Fe dissolution in the solder bath

Using a solder bath made of SUS304 with a volume of 30 L, 40 kg of the solder alloys listed in Tables 1 to 5 were put in, and stirred and heated at 280° C. for 12 hours. After heating and stirring, the molten solder in the solder bath was cooled, and the increase in Fe content was measured by elemental analysis using ICP-AES (Inductively Coupled Plasma Emission Spectroscopy).

When the increase in Fe content by heating and stirring was less than 20 ppm/12h, it was evaluated as "◯", and when it was 20 ppm/12h or more, it was evaluated as "×".

2. Inhibition of precipitation of needle crystals

Melt the solder alloys listed in Tables 1 to 5 at 250°C and cool within 1 minute to 100°C below the solidus temperature of the entire alloy composition. end. In the cross-sectional SEM photograph of the solder alloy after cooling, the range of 300 μm×300 μm was taken at any three places, and the presence or absence of needle crystals derived from the SnFe compound was confirmed. The needle crystal in this example means a crystal having an aspect ratio of 2 or more in one SnFe compound.

When no needle-like crystals were observed at any of the three locations, the evaluation was "◯", and when at least one needle-like crystal was observed, the evaluation was "x".

3. IMC growth inhibition for Cu

The Bare-Cu board coated with the liquid flux was immersed in molten solder having the alloy compositions shown in Tables 1 to 5 heated to 280° C., to produce a solder-plated Cu board. This solder-plated Cu board was heat-processed for 300 hours on the hot plate heated to 150 degreeC. In the SEM photograph of the cross-section of the cooled solder alloy, the maximum crystal grain size of the intermetallic compound is determined at any three places in the range of 300 μm × 300 μm.

In this embodiment, the so-called maximum crystal grain size refers to visually selecting the largest crystal grain among the metal compounds identified from the obtained image, and drawing parallel 2 lines so that the distance between the selected crystal grains becomes the largest. tangent lines, and set their intervals to the maximum grain size.

When the maximum value of the crystal grain size was less than 5 μm, it was evaluated as “◯”, and when the maximum value was 5 μm or more, it was evaluated as “×”.

4. SnCuNi formation suppression in the bump

In the same manner as in the above "3.", a solder-plated Cu plate was prepared to be the same as the above "3." Observe any 3 places on the interface between the Cu plate and the solder alloy in the same way to confirm the presence or absence of SnCuNi-based compounds in the solder alloy. In all locations, when the formation of the SnCuNi-based compound was not observed near the interface of the solder alloy, it was evaluated as "◯", and when the formation of the SnCuNi-based compound was observed at least one place, it was evaluated as "×".

5. Surface Concentration of As

The presence or absence of an As concentration layer was evaluated as follows using depth direction analysis by XPS (X-ray photoelectron spectroscopy: X-ray Photoelectron Spectroscopy).

(analysis conditions)

． Analytical device: Micro-area X-ray photoelectron spectroscopic analysis device (AXIS Nova manufactured by Kratos Analytical Co., Ltd.)

． Analysis conditions: X-ray source AlKα line, X-ray gun voltage 15kV, X-ray gun current value 10mA, analysis area 700μm×300μm

． Sputtering conditions: ion species Ar ⁺ , accelerating voltage 2kV, sputtering rate 0.5nm/min (SiO ₂ conversion)

． Samples: Prepare 3 solder powders having the alloy compositions shown in Tables 3-5, spread flatly and without gaps on the stage with carbon tape attached, as samples. Among them, the size of the sample is set to 5.0 mm×5.0 mm. The solder powder used has an average particle diameter of 21 μm, which corresponds to JIS Z3284-1:2014 powder size classification (Table 2) of 5, and was obtained by heating at 60° C. for 30 minutes using a drying device in the atmosphere. In Comparative Example 8, no heat treatment was performed.

(Evaluation order)

From a sample with a size of 5.0mm×5.0mm, select an arbitrary area of 700μm×300μm, carry out XPS analysis on each atom of Sn, O and As while performing ion sputtering, and obtain an XPS analysis chart. One region is selected for each sample, and each of the three samples is analyzed once for a total of three times.

An example of a graph obtained by XPS analysis is shown in FIGS. 1 to 3 . Figures 1 to 3 are obtained by changing the scale of detection intensity (cps) on the vertical axis for the same sample, and the horizontal axis is the depth (nm) converted to _SiO2 calculated from the sputtering time. In the graph of XPS analysis, the vertical axis is the detection intensity (cps), and the horizontal axis can be selected from the sputtering time (min) or the _SiO2 -converted depth calculated from the sputtering etching rate of the _SiO2 standard sample for the sputtering time ( nm), but in Figures 1 to 3, the horizontal axis in the graph of XPS analysis is the depth (nm) in terms of _SiO2 calculated from the sputtering etching rate of the _SiO2 standard sample for the sputtering time .

In addition, in the graph of XPS analysis of each sample, the depth in conversion of SiO ₂ at which the detection intensity of O atoms becomes the maximum is set as Do. max (nm) (see Figure 2). Then, compare Do. In the deeper portion of max, the depth in terms of SiO ₂ at which the detection intensity of O atoms becomes 1/2 intensity of the maximum detection intensity (intensity at Do.max) is set to D1 (nm).

Next, in the XPS analysis chart of each sample, the ratio of the detection intensity of As in the region from the outermost surface to a depth of 2×D1 (the region where the depth is 0 to 2×D1 (nm) in terms of SiO ₂ ) was obtained. Integral value (S1), and detection of As in the region from the depth of 2×D1 to the part with a depth of only 2×D1 (the region where the depth is 2×D1~4×D1 (nm) in terms of SiO ₂ ) Integral value (S2) of intensity (refer to Fig. 3 ), and compare them.

In addition, evaluation was performed based on the following criteria.

． S1>S2 in all 3 measurements: As concentrated layer formed (○)

． The frequency of 2 or less out of all 3 measurements is S1>S2: No As-concentrated layer was formed (×)

6. Viscosity inhibition

By combining the solder powder obtained from the solder alloys of Examples and Comparative Examples in Tables 3 to 5 and the flux shown in Table 6, the mass ratio of flux to solder powder (flux:solder powder) becomes 11:89. After heated and stirred by the method, it was cooled to prepare a solder paste. For these solder pastes, according to the method described in JIS Z 3284-3:2014 "4.2 Viscosity characteristic test", using a rotational viscometer (PCU-205, manufactured by Malcolm Co., Ltd.), the rotation speed: 10rpm, measurement Temperature: 25°C, continuously measure the viscosity for 12 hours. Then, the initial viscosity (viscosity after stirring for 30 minutes) was compared with the viscosity after 12 hours, and the thickening suppression effect was evaluated based on the following criteria.

Viscosity after 12 hours≦initial viscosity×1.2: Viscosity increase over time is small and good (○)

Viscosity after 12 hours>Initial viscosity×1.2: Viscosity rises greatly over time and is not good (×)

7. Changes in yellowness

Heat solder balls (ball diameter 0.3 mm) with the alloy compositions shown in Tables 3 to 5 in a constant temperature bath at 200°C for 2 hours. For the yellowness b* in the L*a*b* color system, measure the solder balls before and after heating, and calculate the increase (△b*) from the b* after heating minus the b* before heating ). Only in Comparative Example 8, solder balls that were not heat-treated were introduced into the constant temperature bath.

The yellowness b* is measured using a CM-3500d2600d spectrophotometer (manufactured by Konica Minolta Corporation), in a D65 light source and a 10-degree field of view, in accordance with JIS Z 8722: 2009 "Color determination method - reflection and penetration objects Color" is used to measure the spectral transmittance, which is obtained from the color value (L*, a*, b*). Still, the color values (L*, a*, b*) are based on the standard of JIS Z 8781-4:2013.

The value of △b* is less than 70% of △b* (standard): ○ (good)

The value of △b* is greater than 70% of △b* (baseline): × (poor)

8. Solder wettability

Regarding the solder paste produced in the same way as in "6." above, print each solder paste immediately after production on a Cu board, and heat up from 25°C at a rate of 1°C/s in a _N2 environment in a reflow furnace. After heating to 260°C, it was cooled to room temperature. Wettability was evaluated by observing the appearance of the cooled solder bumps with an optical microscope. When incompletely melted solder powder was not observed, it was rated as "◯", and when incompletely melted solder powder was observed, it was rated as "x".

The results of the evaluation are shown in Tables 1-5.

As shown in Tables 1 to 5, it can be seen that any alloy composition of Examples 1 to 100 satisfies all the requirements of the present invention, so the elution of Fe in the solder bath is suppressed, the precipitation of needle crystals is suppressed, and the resistance to Cu is suppressed. IMC growth, suppression of SnCuNi formation in bumps. In addition, regarding the examples containing As in Tables 3 to 5, it was further confirmed that the surface of As was concentrated, and it was found that the thickening of the solder paste and the change of the yellowness of the solder alloy were suppressed, and excellent solder wettability was exhibited.

On the other hand, in any of the alloy compositions of Comparative Examples 1 to 7 and Comparative Examples 9 to 15, at least one of the requirements of the present invention is not satisfied, so the dissolution of Fe in the solder bath is suppressed, the precipitation of needle crystals is suppressed, At least one of IMC growth inhibition for Cu, SnCuNi formation inhibition in the bump is poor. In Comparative Example 8, since no heat treatment was performed, concentration of As on the surface was not confirmed, and it was found that thickening of the solder paste could not be suppressed, and the solder alloy was yellowed.

Claims (8)

A solder alloy characterized in that it has Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, and the rest is Sn in terms of mass %. A solder alloy characterized by: Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, Ag: 0-4.0%, and others in mass % Part of it is composed of Sn alloy. A solder alloy characterized by: Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, As: 0.0040-0.0250%, and others in mass % Part of it is composed of Sn alloy. A solder alloy characterized by: Cu: 0.55-0.75%, Ni: 0.0350-0.0600%, Ge: 0.0035-0.0200%, Fe: 0.0020-0.0100%, Ag: 0-4.0%, As: 0.0040~0.0250%, and the rest is an alloy composition of Sn. The solder alloy according to any one of claims 1 to 4, wherein the aforementioned alloy composition further satisfies at least one of the following formulas (1) to (5); 0.0430(%)≦Ni+Fe≦0.0700(%) ( 1) 3.50≦Ni/Fe≦30.00 (2) 10.83≦Cu/Ni≦18.57 (3) 65.00≦Cu/Fe≦325.00 (4) 0.0060(%)≦Ge+Fe≦0.0280(%) (5) In the formulas (1) to (5) above, Ni, Fe, Cu, and Ge represent the contents (% by mass) of the aforementioned alloy compositions. A solder paste comprising solder powder and flux made of the solder alloy according to any one of Claims 1 to 5. A solder ball, which is made of the solder alloy according to any one of Claims 1-5. A solder preform made of the solder alloy according to any one of Claims 1-5.

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