TWI781331B - Flux Materials, Solder Paste, and Solder Joints - Google Patents

Abstract

An object of the present invention is to provide a solder material, solder paste, and solder joint that can suppress the increase in viscosity over time and have excellent wettability and reliability. The flux material of the present invention is characterized in that it contains Sn or a Sn-based alloy, 40-250 mass ppm of As, and 20 mass ppm-0.7 mass % of Pb, and has an As-concentrated layer.

Description

Solder materials, solder paste, and solder joints

The invention relates to a flux material, a solder paste, and a flux joint.

Fixing and electrical connection of electronic parts in electronic equipment such as mounting of electronic parts to printed circuit boards are generally performed by soldering which is most advantageous in terms of cost and reliability.

Solder materials generally contain Sn as the main component, so Sn reacts with oxygen in the air during or after manufacture, forming a film of Sn oxide on the surface, resulting in yellowing.

As a method of improving the discoloration of the flux material, it is known to add elements such as P, Ge, and Ga to the flux material. Compared with Sn, the standard free energy of formation of oxides of these elements is smaller, and they are very easy to be oxidized. Therefore, when a flux material such as flux powder or solder ball is formed from molten flux, elements such as P, Ge, Ga, etc. are oxidized and concentrated on the surface instead of Sn, and yellowing of the flux surface can be suppressed. However, in general, solder materials are required to spread on metals of electronic parts (wettability) when molten, so when elements such as P, Ge, and Ga are added, the wettability of the solder materials decreases. If the wettability of the flux material is poor, it will become the cause of poor soldering.

In addition, among soldering, soldering using solder paste is most commonly performed because it is advantageous in terms of cost and reliability in bonding and assembling electronic components to a substrate of an electronic device. Solder paste is a mixture made by kneading flux material (flux powder) and flux containing components other than flux material such as rosin, activator, thixotropic agent, and solvent. The application of the solder paste to the substrate is performed, for example, by screen printing using a metal mask. Therefore, in order to ensure the printability of the solder paste, the viscosity of the solder paste must be moderate. However, generally speaking, the storage stability of solder paste is poor, and the viscosity of solder paste may increase over time.

Furthermore, in the flux material constituting the solder paste, if the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) (ΔT = T _L - T _S ) becomes large, the After the substrate is solidified, the structure of the flux material tends to become uneven, which will reduce future reliability.

As a solder material containing Pb, for example, a solder alloy powder for bumps has been proposed. ppm of Pb, and the remainder contains Sn and unavoidable impurities (Patent Document 1). However, the flux material described in Patent Document 1 is aimed at suppressing protrusions generated during bump formation, and does not improve problems of discoloration or viscosity increase over time when it is made into a solder paste.

As described above, there is a demand for a flux material that can suppress discoloration or increase in viscosity over time when it is made into a paste, and that is also excellent in wettability and reliability. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-237088

[Problem to be solved by the invention]

It is an object of the present invention to provide a flux material that has less discoloration or a viscosity increase over time when it is made into a paste, and has excellent wettability and reliability. [Technical means to solve the problem]

The inventors of the present invention conducted earnest research in order to solve the above-mentioned problems, and as a result, found that the discoloration of the flux material having an As-concentrated layer on the surface side or the change over time in the viscosity when it is made into a paste is small, and that the flux material containing As is less. Generally, there is a tendency for the wettability to decrease, but if an As concentration layer is formed on the surface, there is no such decrease in wettability. It is known that the above-mentioned problems can be solved by using this material, and this paper was completed. invention. That is, specific aspects of the present invention are as follows. Furthermore, in this specification, when "~" is used to indicate a numerical range, the range includes numerical values at both ends. Moreover, the content of each element can be measured by analyzing with ICP-AES (inductively coupled plasma-atomic emission spectrometry, inductively coupled plasma-atomic emission spectrometry) based on JIS Z 3910, for example.

[1] A flux material comprising Sn or a Sn-based alloy, 40 to 250 mass ppm of As, and 20 to 0.7 mass % of Pb, and having an As-concentrated layer. [2] The flux material according to [1], wherein the Sn or Sn-based alloy is a Sn-based alloy containing 0.005 to 40% by mass of Ag and/or 0.001 to 10% by mass of Cu. [3] The flux material according to [1] or [2], wherein the form of the flux material is powder. [4] A solder paste comprising the flux material as described in [3], and a flux. [5] The solder paste according to [4], further comprising zirconia powder. [6] The solder paste described in [5], wherein the content of the zirconia powder is 0.05 to 20.0% by mass relative to the entire mass of the solder paste. [7] A solder joint comprising Sn or a Sn-based alloy, 40 to 250 mass ppm of As, and 20 to 0.7 mass % of Pb, and having an As-concentrated layer. [Effect of Invention]

According to the present invention, it is possible to provide a flux material which has less discoloration, good wettability, high reliability such as cycle characteristics, and a small increase in viscosity over time when it is made into a solder paste.

Hereinafter, an embodiment for implementing the present invention (hereinafter referred to as "the present embodiment") will be described. However, this invention is not limited to this, Various changes are possible in the range which does not deviate from the summary.

In this embodiment, the flux material contains Sn or a Sn-based alloy, 40-250 mass ppm of As, and 20 mass ppm-0.7 mass % of Pb.

Here, the purity of Sn is not particularly limited, and for example, those with a purity of 3 N (99.9% or higher), 4 N (99.99% or higher), and 5 N (99.999% or higher) can be used. In addition, examples of the Sn-based alloys include Sn-Ag alloys, Sn-Cu alloys, Sn-Ag-Cu alloys, Sn-Ag-Cu-Ni-Co alloys, Sn-In alloys, Sn-Bi alloys, and Sn-Sb alloys. Alloys or alloys obtained by adding Ag, Cu, In, Ni, Co, Sb, Bi, Ge, P, Fe, Zn, Al, Ga, etc. to the above alloy composition. The content of Sn in the Sn-based alloy is not limited, and may be, for example, more than 40% by mass. Furthermore, Sn and Sn-based alloys may also contain unavoidable impurities.

In this embodiment, the Sn-based alloy preferably contains 0.005 to 40% by mass of Ag and/or 0.001 to 10% by mass of Cu and The rest are Sn. In this case, from the viewpoint of ΔT, the content of Ag with respect to the entire mass of the solder material is preferably 4% by mass or less. When the content of Ag exceeds 3.8% by mass, ΔT tends to increase significantly. The content of Ag relative to the mass of the entire flux material is more preferably 0.1 to 3.8% by mass, most preferably 0.5 to 3.5% by mass. In addition, from the viewpoint of ΔT, the content of Cu with respect to the mass of the entire flux material is preferably 1.0% by mass or less. When the content of Cu exceeds 0.9% by mass, ΔT tends to increase significantly. The content of Cu relative to the mass of the entire flux material is more preferably 0.05 to 0.9% by mass, most preferably 0.1 to 0.7% by mass. Furthermore, the preferred numerical ranges of the above-mentioned Ag and Cu contents are independent, and the Ag and Cu contents can be determined independently.

In this embodiment, the content of As relative to the mass of the entire flux material is 40-250 mass ppm (0.0040-0.0250 mass %), preferably 50-150 mass ppm, more preferably 50-100 mass ppm. If the As content is less than 40 mass ppm, it will be extremely difficult to form an As concentrated layer. If As satisfies the condition that the content of As is 40 to 250 mass ppm relative to the mass of the entire flux material, and there is an As concentrated layer in the flux material, part or all of it can form an alloy (intermetallic compound) together with Sn or a Sn-based alloy. Or solid solution, etc.), can also be separated from the Sn-based alloy, for example, exist as a single component of As or as an oxide.

In this embodiment, content of Pb with respect to the mass of the whole flux material is 20 mass ppm - 0.7 mass % (0.002-0.7 mass %). It was found that when Pb is sufficiently present, there is a tendency to suppress the increase in viscosity. The reason for this is not clear, but it is considered that the reason is that since Pb is a relatively noble metal compared to Sn, the Sn—Pb alloy is less likely to be ionized than Sn, and is less likely to be eluted into the flux as an ionic state (salt). However, the mechanism does not depend on this. On the other hand, if the content of Pb is too large, the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) (ΔT=T _L -T _S ) will increase, which will reduce the reliability of the cycle characteristics. Yu. From such a viewpoint, the content of Pb is preferably from 0.005 to 0.7% by mass, more preferably from 0.01 to 0.5% by mass, with respect to the entire mass of the solder material. If Pb satisfies the condition that the content of Pb is 20 mass ppm to 0.7 mass % relative to the overall mass of the flux material, it may form an alloy (intermetallic compound or solid solution, etc.) The Sn-based alloy exists separately.

In this embodiment, the flux material has an As concentrating layer in at least a part thereof. Here, the As-concentrated layer refers to a region where the As concentration is higher than the average As concentration in the solder material (the content of As relative to the overall mass of the solder material), and specifically, its existence can be confirmed by the criteria for determination described later. The As concentration layer is preferably present on at least a part of the surface side of the solder material, and more preferably covers the entire surface.

(Criteria for judging) Prepare a sample with a size of 5.0 mm x 5.0 mm (if the solder material is not in the form of a plate, the solder material (solder powder, solder ball, etc.) (obtained by conglomeration), select an arbitrary area of 700 μm×300 μm, and perform XPS analysis using ion sputtering. One region is selected for each sample, and three samples are analyzed once each, for a total of three times. When the size relationship between S1 and S2 described later is consistent in all three analyzes (when the As concentration layer exists on the surface side, it is the case that S1 > S2 in all three analyzes), it is judged to be formed There is an As concentrated layer. Here, the definitions of S1, S2 and D1 are as follows. S1: In the line graph of the XPS analysis performed on the above sample, the integrated value of the detection intensity of As in the region where the SiO ₂ converted depth is 0 to 2×D1 (nm) S2: In the XPS analysis performed on the above sample In the line graph, the integral value D1 of the detection intensity of As in the region where the SiO ₂ conversion depth is 2×D1～4×D1 (nm): in the line graph of the XPS analysis performed on the above sample, at In the deep part where the detection intensity of atoms becomes the maximum _SiO2 equivalent depth (Do・max(nm)), the detection intensity of O atoms becomes 1/2 of the maximum detection intensity (the intensity at Do・max) at the beginning Depth (nm) in terms of SiO ₂ (refer to Figure 3). However, the detailed conditions of the XPS analysis in this criterion are as described in "(1) Evaluation of the presence or absence of an As-concentrated layer" described later. Furthermore, in this judgment standard, it is premised that D1 can be defined, that is, the detection intensity of O atoms in the XPS analysis line diagram takes the maximum value. In the case where D1 cannot be defined (the detection intensity of O atoms is always fixed, etc.) ), it was judged that the As-concentrated layer did not exist.

If there is an As concentration layer, it is not clear why the problems of discoloration, wettability, and viscosity increase when it is made into solder paste are not clear, but it is considered that the increase in viscosity is due to the interaction between Sn or Sn oxide and solder paste ( It is caused by the reaction between various additives such as activators contained in the flux) to form a salt, or the aggregation of the flux material, etc. Therefore, it is considered that the reason is that if there is an As concentration layer on the surface of the flux material, As Concentration The chemical layer is interposed between the flux alloy and the flux, and the above-mentioned reaction is not easy to occur. However, the mechanism does not depend on this.

In this embodiment, the thickness of the As-concentrated layer (in terms of SiO ₂ ) is not limited, but is preferably 0.5-8.0 nm, more preferably 0.5-4.0 nm, most preferably 0.5-2.0 nm. Here, the thickness of the As concentrated layer refers to 2×D1. When the thickness of the As concentration layer is within the above range, it is possible to sufficiently suppress discoloration and an increase in viscosity over time when it is made into a solder paste without adversely affecting wettability.

The flux material of this embodiment can suppress discoloration or viscosity of solder paste over time by making the content of As and Pb relative to the mass of the entire flux material within the above-mentioned range, and including an As-concentrated layer in the flux material. rise, and excellent wettability and reliability.

The manufacturing method of the flux material of this embodiment is not limited, It can manufacture by melt-mixing raw material metal. The method of forming the As concentration layer in the solder material is also not limited. As an example of the formation method of an As concentration layer, heating a flux material in an oxidation atmosphere (air or oxygen atmosphere) is mentioned. 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 at least 10 minutes, more preferably at least 20 minutes.

In this embodiment, the form of the flux material is not particularly limited, and may be in the form of a rod such as a solder rod, a wire, or particles such as solder balls or solder powder. When the flux material is in the form of particles, the fluidity of the flux material is improved.

The method of producing the granular flux material is not limited, and known methods such as a dropping method of dripping molten flux material to obtain particles, a spray method of centrifugal spraying, and a method of pulverizing bulk flux material can be used. In the dropping method or the spraying method, in order to form particles, the dropping or spraying is preferably performed in an inert atmosphere or in a solvent.

In addition, when the flux material is in the form of particles, if it has a size (particle size distribution) corresponding to the number 1 to 8 in the powder size classification (Table 2) in JIS Z 3284-1:2004, it can be realized. Welding of micro parts. The size of the particulate flux material is more preferably the size corresponding to the number 4-8, and more preferably the size corresponding to the number 5-8. When the flux material is granular, the true sphericity is preferably at least 0.90, more preferably at least 0.95, and most preferably at least 0.99.

In this embodiment, the usage form of the flux material is not particularly limited. For example, it can be mixed with fats and oils to make resin cored flux, and when the flux material is in powder form, it can also be mixed with flux containing rosin-based resins, activators, solvents, etc. to use as solder paste, or as a Solder balls are used, but the flux material of this embodiment has a small increase in viscosity over time when it is made into a solder paste, so it is particularly suitable for use as a solder paste.

In this embodiment, the solder paste contains the flux powder and flux of this embodiment. Here, "flux" refers to all components in the solder paste except flux powder, and the mass ratio of flux powder to flux (solder powder:flux) is not limited and can be appropriately set according to the application.

In this embodiment, the composition of the soldering flux is not limited, for example, it may include various additives such as resin components, solvents, activators, thixotropic agents, pH regulators, antioxidants, colorants, defoamers, etc. in any ratio. . Resins, solvents, and various additives are also not limited, and general users of solder paste can be used. Preferable specific examples of the activator include organic acids, amines, halogens (organic halogen compounds, amine hydrohalides), and the like.

In this embodiment, the solder paste may further include zirconia powder. The content of the zirconia powder relative to the overall mass of the solder paste is preferably 0.05-20.0% by mass, more preferably 0.05-10.0% by mass, most preferably 0.1-3% by mass. If the content of the zirconia powder is within the above range, the activator contained in the flux reacts preferentially with the zirconia powder, and the reaction with Sn or Sn oxide on the surface of the flux powder is less likely to occur, thereby further suppressing the effect of aging. The effect of the viscosity increase caused by the change.

There is no upper limit on the particle size of the zirconia powder added to the solder paste, but it is preferably 5 μm or less. If the particle size is 5 μm or less, the printability of the paste can be maintained. Also, the lower limit is not particularly limited, but is preferably 0.5 μm or more. The above-mentioned particle size is taken as a SEM (scanning electron microscope, scanning electron microscope) photo of zirconia powder. When the projected circle equivalent diameter is obtained by image analysis for each particle existing in the field of view, the projected circle equivalent diameter is 0.1 The average value of the projected circle equivalent diameter of those above μm. The shape of the zirconia particles is not particularly limited, and if it is of a different shape, the contact area with the flux will be larger, and it will have the effect of suppressing the increase of viscosity. If it is spherical, good fluidity can be obtained, so excellent printability as a paste can be obtained. What is necessary is just to select a shape suitably according to the required characteristic.

In the present embodiment, the solder paste can be produced by kneading the flux material (flux powder) and flux according to the present embodiment by a known method. The solder paste in this embodiment can be used for, for example, a circuit board with a fine structure in an electronic device. Specifically, it can be printed by a printing method using a metal mask, a discharge method using a dispenser, or a transfer needle. method, etc., apply to the welded part, and perform reflow.

In this embodiment, the flux material can be used as a joint (joint portion) for joining two or more various members. The joining member is not limited, for example, it is also useful as a joint of an electronic equipment member. In this embodiment, the solder joint contains Sn or a Sn-based alloy, 40-250 mass ppm of As, and 20 mass ppm-0.7 mass % of Pb, and at least a part thereof contains an As-concentrated layer. The solder joint of this embodiment can have the same composition and physical properties as the above-mentioned flux material of this embodiment, and can be formed using the above-mentioned flux material of this embodiment. When the content of As and Pb with respect to the mass of the whole solder joint is within the above-mentioned range, and when the As concentrated layer is included in the solder joint, it becomes a solder joint with no discoloration and excellent reliability.

In this embodiment, the solder joint can be manufactured by, for example, a common method in the industry, such as disposing or applying solder balls containing the flux material of this embodiment or the solder paste of this embodiment on portions to be joined and heating.

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited to the contents described in the examples. [Example]

(Evaluation) For the flux powders of Examples and Comparative Examples, (1) evaluation of the presence or absence of an As concentrated layer, (2) evaluation of inhibition of thickening, (3) evaluation of solder wettability, (4) Evaluation of reliability.

(1) Evaluation of the presence or absence of an As concentrating layer The presence or absence of an As concentrating layer was evaluated as follows using depth direction analysis by XPS (X-ray photoelectron spectroscopy: X-ray Photoelectron Spectroscopy). (Analysis conditions) ・Analysis device: Micro-area X-ray photoelectron spectroscopy analyzer (AXIS Nova manufactured by Kratos Analytical Co., Ltd.) ・Analysis conditions: X-ray source is AlKα rays, X-ray gun voltage is 15 kV, X-ray gun current is 10 mA, analysis area 700 μm×300 μm ・Sputtering conditions: Ar ⁺ ion species, accelerating voltage 2 kV, sputtering rate 0.5 nm/min (SiO ₂ conversion) ・Samples: Prepare 3 samples A sample obtained by spreading the flux material (flux powder in Examples and Comparative Examples) on the stage of the carbon ribbon without gaps was used. Among them, the size of the sample is set at 5.0 mm×5.0 mm. (Evaluation procedure) Select an arbitrary area of 700 μm x 300 μm from a sample with a size of 5.0 mm x 5.0 mm, perform XPS analysis on each atom of Sn, O, and As while performing ion sputtering, and obtain the results of the XPS analysis line graph. One region is selected for each sample, and three samples are analyzed once each, for a total of three times. An example of the line graph obtained by XPS analysis is shown in FIGS. 1 to 3 . Figures 1 to 3 are obtained by changing the scale of the 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 line 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 conversion calculated from the sputtering etching rate of the _SiO2 standard sample for the sputtering time Any depth (nm), but in Figures 1 to 3, the horizontal axis in the XPS analysis line graph is set to the _SiO2 conversion calculated from the sputtering etching rate of the _SiO2 standard sample for the sputtering time Depth (nm). In addition, in the line graph of XPS analysis of each sample, the depth in terms of SiO ₂ at which the detection intensity of O atoms becomes the maximum is defined as Do·max (nm) (see FIG. 2 ). Then, in the part deeper than Do・max, the detection intensity of O atoms becomes 1/2 of the maximum detection intensity (intensity at Do・max) in the first _SiO2 -converted depth is set to D1 (nm) . Next, in the line graph of the XPS analysis of each sample, the ratio of the detection intensity of As in the region from the outermost surface to the depth of 2×D1 (the depth of _SiO2 conversion is 0 to 2×D1 (nm)) is obtained. Integral value (S1) and the integral of detection intensity of As in the region from the depth of 2×D1 to the part as deep as 2×D1 (the region with a depth of 2×D1 to 4×D1 (nm) in terms of SiO ₂ ) value (S2) (refer to Figure 3), and compare them. Then, evaluation was performed based on the following criteria.・S1>S2 in all 3 measurements: As-concentrated layer formed (○) ・S1>S2 in 2 or less of all 3 measurements: As-concentrated layer not formed (×)

(2) Evaluation of viscosity increase inhibition After each material of the composition shown in the following Table 1 was heated and stirred, it cooled, and the flux was prepared. Solder paste was produced by kneading the prepared flux and the flux powder of each of Examples and Comparative Examples so that the mass ratio of the flux and the flux powder (flux:flux powder) would be 11:89.

[Table 1]

For the obtained solder paste, according to the method described in "4.2 Viscosity characteristic test" of JIS Z 3284-3, use a rotational viscometer (PCU-205, manufactured by Malcom Co., Ltd.) at a rotation speed of 10 rpm and a measurement temperature of: At 25°C, continue to 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 increases over time and is not good (×)

(3) Evaluation of solder wettability In the same manner as in the above-mentioned "(2) Evaluation of thickening suppression", solder paste was produced using the flux powders of each of the examples and comparative examples. Use a metal mask with an opening diameter of 6.5 mm, a number of openings of 4, and a mask thickness of 0.2 mm to print the obtained solder paste on a Cu board, and in a reflow furnace under N ₂ atmosphere at 1 °C The heating rate of /sec is from 25°C to 260°C, and then cooled to room temperature (25°C) in air to form 4 solder bumps. The external appearance of the obtained solder bump was observed using an optical microscope (magnification: 100 times), and it evaluated based on the following reference|standard. Incompletely melted flux particles were not observed in any of the four solder bumps. : Solder wettability is good (◯) Incompletely melted flux particles were observed in one or more of the four solder bumps. : Poor flux wettability (×)

(4) Evaluation of reliability For the flux powders of Examples and Comparative Examples, use a differential scanning calorimeter (EXSTAR DSC7020, manufactured by SII Nano Technologies Co., Ltd.) at a heating rate of 5°C/min (180°C to 250°C). ℃), cooling rate: -3℃/min (250℃～150℃), carrier gas: N ₂ under the conditions of DSC (Differential Scanning Calorimetry, Differential Scanning Calorimetry) measurement, liquidus temperature (T _L ) and solidus temperature (T _S ). Then, the difference (ΔT=T _L -T _S ) between the liquidus temperature (T _L ) and the solidus temperature (T _S ) was calculated, and the evaluation was performed based on the following criteria. ΔT within 10°C: excellent reliability (○) ΔT over 10°C: poor reliability (×) The difference between the liquidus temperature (T _L ) and solidus temperature (T _S ) of the solder powder (ΔT=T When _L - T _S ) is large, when the solder paste containing the flux powder is applied to the substrate of the electronic device and then solidified, structures with a higher melting point tend to precipitate on the surface of the flux powder. If the structure with higher melting point precipitates on the surface of the flux powder, then the structure with lower melting point gradually precipitates to the inside of the flux powder, which will cause the structure of the flux powder to become uneven and reduce the reliability of the cycle.

(Examples A1 to A35, Comparative Examples A1 to A12) Sn, As, and Pb were weighed so that the content of As and Pb became as shown in Table 2 below, and Sn became the rest (the total of Sn, As, and Pb became the rest of 100% by mass), and melt-mixed, Centrifugal spraying was performed in an Ar atmosphere to prepare a powder (average particle size: 21 μm, corresponding to JIS Z3284-1:2004 powder size classification (Table 2) 5). The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. However, for Comparative Examples A1 to A6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole flux material, and content of Pb is mass % with respect to the mass of the whole flux material. Also, as Sn, a 3N material containing unavoidable impurities is used.

(Examples B1-B35, Comparative Examples B1-B12) Weighed so that the content of Cu becomes 0.7% by mass, the content of As and Pb becomes as shown in Table 3 below, and the rest of Sn (the total of Sn, As, Pb, and Cu becomes the rest of 100% by mass) Sn, As, Pb, and Cu were melt-mixed and centrifugally sprayed in an Ar atmosphere to prepare powder (average particle size 21 μm, powder size classification 5). The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. However, for Comparative Examples B1 to B6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole flux material, and content of Pb and Cu is mass % with respect to the mass of the whole flux material. Also, as Sn, a 3N material containing unavoidable impurities is used.

(Examples C1-C35, Comparative Examples C1-C12) When the content of Cu is 0.5% by mass, the content of Ag is 1.0% by mass, the content of As and Pb is as shown in Table 4 below, and Sn is the rest (the total of Sn, As, Pb, Ag, and Cu is 100 Sn, As, Pb, Ag, and Cu were weighed by the method of mass %, melted and mixed, and centrifugally sprayed in Ar atmosphere to prepare powder (average particle size 21 μm, powder size classification 5) . The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. Among them, for Comparative Examples C1 to C6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole solder material, and content of Pb, Ag, and Cu is mass % with respect to the mass of the whole solder material. Also, as Sn, a 3N material containing unavoidable impurities is used. For the flux powder obtained in Example C1, the contents of Sn, As, Pb, Ag, and Cu were analyzed by ICP-AES according to JIS Z 3910, and the results confirmed that they were consistent with the added amounts.

(Examples D1-D35, Comparative Examples D1-D12) The content of Cu is 0.5% by mass, the content of Ag is 2.0% by mass, the content of As and Pb is as shown in the following Table 5, and the rest is Sn (the total of Sn, As, Pb, Ag and Cu is 100 Sn, As, Pb, Ag, and Cu were weighed by the method of mass %, melted and mixed, and centrifugally sprayed in Ar atmosphere to prepare powder (average particle size 21 μm, powder size classification 5) . The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. Among them, for Comparative Examples D1 to D6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole solder material, and content of Pb, Ag, and Cu is mass % with respect to the mass of the whole solder material. Also, as Sn, a 3N material containing unavoidable impurities is used.

(Examples E1-E35, Comparative Examples E1-E12) When the content of Cu is 0.5% by mass, the content of Ag is 3.0% by mass, the content of As and Pb is as shown in Table 6 below, and the rest is Sn (the total of Sn, As, Pb, Ag, and Cu is 100 Sn, As, Pb, Ag, and Cu were weighed by the method of mass %, melted and mixed, and centrifugally sprayed in Ar atmosphere to prepare powder (average particle size 21 μm, powder size classification 5) . The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. Among them, for Comparative Examples E1 to E6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole solder material, and content of Pb, Ag, and Cu is mass % with respect to the mass of the whole solder material. Also, as Sn, a 3N material containing unavoidable impurities is used.

(Examples F1 to F35, Comparative Examples F1 to F12) When the content of Cu is 0.5% by mass, the content of Ag is 3.5% by mass, the content of As and Pb is as shown in Table 7 below, and Sn is the rest (the total of Sn, As, Pb, Ag, and Cu is 100 Sn, As, Pb, Ag, and Cu were weighed by the method of mass %, melted and mixed, and centrifugally sprayed in Ar atmosphere to prepare powder (average particle size 21 μm, powder size classification 5) . The obtained powder was heated in air at 60° C. for 30 minutes using a drying device to obtain flux powders of Examples and Comparative Examples. Among them, for Comparative Examples F1 to F6, heat treatment was not applied, and the powder obtained by centrifugal spraying was directly used as flux powder. In addition, in the following table|surface, content of As is mass ppm with respect to the mass of the whole solder material, and content of Pb, Ag, and Cu is mass % with respect to the mass of the whole solder material. Also, as Sn, a 3N material containing unavoidable impurities is used.

(1) Evaluation of the presence or absence of an As concentration layer, (2) evaluation of inhibition of thickening, (3) evaluation of solder wettability, and (4) evaluation of reliability of the flux powders of Examples and Comparative Examples The results of the evaluation are shown in Tables 2 to 7 below.

[表2-2]

[table 2-1]

[Table 2-2]

[表3-2]

[Table 3-1]

[Table 3-2]

[表4-2]

[Table 4-1]

[Table 4-2]

[表5-2]

[Table 5-1]

[Table 5-2]

[表6-2]

[Table 6-1]

[Table 6-2]

[表7-2]

[產業上之可利用性][Table 7-1]

[Table 7-2]

[Industrial availability]

The flux material of the present invention can be used in various applications because it has no discoloration and is excellent in reliability such as flux wettability and cycle characteristics. Used as a flux material for solder paste.

Fig. 1 is an example of a line diagram of XPS (X-ray photoelectron spectroscopy, X-ray photoelectron spectroscopy) analysis on the surface of a solder material. Fig. 2 is an example of a line diagram of XPS analysis of the surface of a solder material. Fig. 3 is an example of a line diagram of XPS analysis of the surface of a solder material.

Claims (5)

A solder alloy comprising 40-250 mass ppm of As and 20 mass ppm-0.7 mass % of Pb, the remainder being Sn, and having an As-concentrated layer confirmed by the following criteria on the surface; (criteria ) in a sample with a size of 5.0mm×5.0mm, select any area of 700μm×300μm from it, and perform XPS analysis with ion sputtering; select 1 area for each sample, and conduct 1 time for each of the 3 samples , a total of 3 times of analysis; in all 3 times of analysis, when S1>S2 is the case, it is judged that there is an As concentrated layer; here, S1: in the line diagram of XPS analysis, the depth converted to _SiO2 is Integral value of the detection intensity of As in the region of 0~2×D1(nm); S2: In the line diagram of XPS analysis, the depth converted from SiO ₂ is in the region of 2×D1~4×D1(nm) Integral value of the detection intensity of As; D1: In the line diagram of XPS analysis, the detection of O atoms 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 initial _SiO2 -converted depth (nm) at which the intensity becomes 1/2 of the intensity of the maximum detection intensity (the intensity at Do‧max); moreover, in the XPS analysis line diagram, the detection intensity of the O atom does not reach the maximum When the value of D1 cannot be defined, it is judged that the As-concentrated layer does not exist. The solder alloy according to claim 1, further comprising 0-3.5% by mass of Ag and/or 0-0.7% by mass of Cu. The flux alloy according to claim 1 or 2, wherein the form of the above-mentioned flux alloy is powder. A solder paste, comprising the solder alloy according to claim 3, and flux. A solder joint formed of the solder alloy according to any one of Claims 1 to 3.

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