JP6691305B2 - Solder materials, solder pastes, and solder joints - Google Patents

Description

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

  Fixing and electrical connection of electronic components in an electronic device such as mounting of electronic components on a printed circuit board are generally performed by soldering, which is most advantageous in terms of cost and reliability.

  Although the solder material generally contains Sn as a main component, Sn may react with oxygen in the air during or after the manufacture to form a film of Sn oxide on the surface, causing yellow discoloration.

  As a method for improving the discoloration of the solder material, it is known to add an element such as P, Ge or Ga to the solder material. These elements have a smaller standard free energy of formation of oxide than Sn and are very easily oxidized. Therefore, when forming a solder material such as a solder powder or a solder ball from the molten solder, an element such as P, Ge, or Ga, not Sn, is oxidized and concentrated on the surface, and the yellow change of the solder surface can be suppressed. it can. However, in general, a solder material is required to have a property (wetting property) of spreading on a metal of an electronic component when melted. However, when an element such as P, Ge or Ga is added, the solder material is The wettability of the will decrease. Poor wettability of the solder material causes defective soldering.

Further, among soldering, soldering using a solder paste is advantageous in terms of cost and reliability in joining and assembling electronic components to a substrate of an electronic device, and is most commonly performed. The solder paste is a mixture formed by kneading a solder material (solder powder) and a flux containing components other than the solder material such as rosin, an activator, a thixotropic agent, and a solvent to form a paste.
The application of the solder paste to the substrate is performed by screen printing using a metal mask, for example. Therefore, in order to secure the printability of the solder paste, the viscosity of the solder paste needs to be appropriate. However, in general, the solder paste has poor storage stability, and the viscosity of the solder paste may increase with time.

Further, in the solder material forming the solder paste, the difference between the liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T S) increases, the substrate of the electronic device After application, when solidifying, the structure of the solder material is likely to be non-uniform, which may cause deterioration in future reliability.

Examples of the solder material containing Bi include Ag: 2.8 to 4.2% by weight, Cu: 0.4 to 0.6% by weight, Bi of 50 to 1000 ppm, and the balance of Sn and inevitable impurities. A solder alloy powder for bumps having the following component composition has been proposed (Patent Document 1).
However, the solder material described in Patent Document 1 has a problem of suppressing protrusions generated during bump formation, and does not improve the problem of discoloration or increase in viscosity over time when used as a solder paste.

  As described above, there is a demand for a solder material that suppresses the problems of discoloration and viscosity increase over time when it is made into a paste, and is also excellent in wettability and reliability.

JP, 2013-237089, A

The present invention, viscosity increase over time when the paste is small, and an object thereof is to provide a solder alloy having excellent wettability and reliability.

The present inventors have made intensive studies to solve the above problems, a solder material having an As-rich layer on the surface side is less change in viscosity over time is when a paste, moreover, the solder containing As Although a material usually tends to have low wettability, it has been found that if an As concentrated layer is formed on the surface, there is no such decrease in wettability, and if such a material is used, The inventors have found that the above problems can be solved and have completed the present invention.
That is, specific embodiments of the present invention are as follows.
In addition, in this specification, when a numerical range is expressed by using “to”, the range includes numerical values at both ends. The content of each element can be measured by, for example, analyzing by ICP-AES in accordance with JIS Z3910.

[1] A solder material containing Sn or a Sn-based alloy, 40 to 250 mass ppm As, and 20 mass ppm to 3 mass% Bi, and having an As concentrated layer.
[2] The solder material according to [1], wherein the Sn or Sn-based alloy is a Sn-based alloy containing 0.005 to 40 mass% Ag and / or 0.001 to 10 mass% Cu.
[3] The solder material according to [1] or [2], wherein the form of the solder material is powder.
[4] A solder paste containing the solder material according to [3] and a flux.
[5] The solder paste according to [3], further including zirconium oxide powder.
[6] The solder paste according to [4], wherein the content of the zirconium oxide powder is 0.05 to 20.0 mass% with respect to the total mass of the solder paste.
[7] A solder joint containing Sn or a Sn-based alloy, 40 to 250 mass ppm As, and 20 mass ppm to 3 mass% Bi, and having an As concentrated layer.

According to the present invention, it is possible to get wet is resistant also good, high reliability such as cycle characteristics, provides a small solder material viscosity increase over time when the solder paste.

It is an example of a chart of XPS analysis of the surface of the solder material. It is an example of a chart of XPS analysis of the surface of the solder material. It is an example of a chart of XPS analysis of the surface of the solder material.

Hereinafter, modes for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described.
However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention.

  In the present embodiment, the solder material contains Sn or a Sn-based alloy, 40 to 250 mass ppm As, and 20 mass ppm to 3 mass% Bi.

Here, the purity of Sn is not particularly limited, and for example, the purity of Sn is 3N (99.9% or more), 4N (99.99% or more), 5N (99.999% or more), and the like. A general one can be used.
In addition, as the Sn-based alloy, Sn-Ag alloy, Sn-Cu alloy, Sn-Ag-Cu alloy, Sn-Ag-Cu-Ni-Co alloy, Sn-In alloy, Sn-Sb alloy and the above alloy composition can be used. Examples of the alloy include Ag, Cu, In, Ni, Co, Sb, Ge, P, Fe, Zn, Al, and Ga. The Sn content in the Sn-based alloy is not limited, but may be, for example, more than 40% by mass.
The Sn and Sn-based alloys may contain inevitable impurities.

In the present embodiment, the Sn-based alloy contains 0.005 to 40 mass% Ag and / or 0.001 to 10 mass% Cu from the viewpoint of solder wettability, melting point, and other physical properties as a solder material, It is preferable that the balance is Sn.
In this case, from the viewpoint of ΔT, the content of Ag with respect to the mass of the entire solder material is preferably 4 mass% or less. When the content of Ag exceeds 3.8% by mass, ΔT tends to significantly increase. The content of Ag with respect to the total mass of the solder material is more preferably 0.1 to 3.8% by mass, and most preferably 0.5 to 3.5% by mass.
From the viewpoint of ΔT, the Cu content is preferably 1.0 mass% or less with respect to the mass of the entire solder material. If the Cu content exceeds 0.9% by mass, ΔT tends to significantly increase. The content of Cu with respect to the total mass of the solder material is more preferably 0.05 to 0.9% by mass, and most preferably 0.1 to 0.7% by mass.
In addition, the above-mentioned preferable numerical ranges of the contents of Ag and Cu are independent, and the contents of Ag and Cu can be independently determined.

In the present embodiment, the content of As with respect to the mass of the entire solder material is 40 to 250 mass ppm (0.0040 to 0.0250 mass%), preferably 50 to 150 mass ppm, and 50 to 100 mass ppm. More preferable. When the As content is less than 40 mass ppm, it is extremely difficult to form an As concentrated layer.
As satisfies the condition that the content with respect to the mass of the entire solder material is 40 to 250 mass ppm, and if the As concentrated layer is present in the solder material, a part or all of it is Sn or Sn-based alloy. An alloy (such as an intermetallic compound or a solid solution) may be formed together therewith, or may be present separately from the Sn-based alloy, for example, as a simple substance of As or an oxide.

In the present embodiment, the content of Bi with respect to the total mass of the solder material is 20 mass ppm to 3 mass% (0.002 to 3 mass%). It was found that when Bi is sufficiently present, the increase in viscosity tends to be suppressed. Although the reason is not clear, Bi is a noble metal with respect to Sn. Therefore, the Sn-Bi alloy is less likely to be ionized than Sn, and the elution as an ionic state (salt) into the flux is less likely to occur. it is conceivable that. However, the mechanism does not depend on this. On the other hand, when the content of Bi is too large difference between the liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T S) increases, the reliability of such cycle characteristics May decrease. From such a viewpoint, the content of Bi with respect to the mass of the entire solder material is preferably 0.005 to 2.5 mass%, and more preferably 0.01 to 1 mass%.
As long as the content of Bi with respect to the total mass of the solder material is 20 mass ppm to 3 mass%, all of Bi constitutes an alloy (such as an intermetallic compound or a solid solution) together with Sn or a Sn-based alloy. Alternatively, a part thereof may be present separately from the Sn-based alloy.

In the present embodiment, the solder material has an As concentrated layer on at least a part thereof. Here, the As concentrated layer refers to a region in which the As concentration is higher than the average As concentration in the solder material (the content of As with respect to the mass of the entire solder material), and specifically, the determination criteria described below. The existence can be confirmed by.
The As concentrated layer is preferably present on at least a part of the front surface side of the solder material, and preferably covers the entire surface.

(Criteria)
Sample with a size of 5.0 mm x 5.0 mm (if the solder material is not plate-shaped, the solder material (solder powder, solder balls, etc.) is spread in a range of 5.0 mm x 5.0 mm without gaps) Is prepared, an arbitrary area of 700 μm × 300 μm is selected, and XPS analysis using ion sputtering is performed. One area is selected for each sample, and analysis is performed three times, once for each of the three samples. When the magnitude relationship between S1 and S2, which will be described later, is the same in all of the three analyzes (when the As concentrated layer is present on the surface side, S1> S2 in all three analyzes). , As is determined to be a concentrated layer.
Here, the definitions of S1, S2 and D1 are as follows.
S1: In the chart of XPS analysis performed on the above-mentioned sample, the integrated value of the detection intensity of As in the region of SiO ₂ conversion depth of 0 to 2 × D1 (nm) S2: Of the XPS analysis performed on the above-mentioned sample In the chart, the integrated value of the detection intensity of As in the region where the SiO ₂ conversion depth is 2 × D1 to 4 × D1 (nm) D1: In the chart of the XPS analysis performed on the above sample, the detection intensity of O atom is in deeper than becomes maximum depth of SiO ₂ in terms (Do · max (nm)) , the first SiO ₂ which detects the intensity of O atoms is 1/2 of the intensity of the maximum detection intensity (intensity at Do · max) Converted depth (nm) (see FIG. 3).
However, the detailed conditions of the XPS analysis in this criterion are according to the description of “(1) Evaluation of presence or absence of As concentrated layer” described later.
In this criterion, D1 can be defined, that is, the detection intensity of O atom has the maximum value in the XPS analysis chart. If D1 cannot be defined (the detection intensity of O atom is always In a constant case), it is determined that the As concentrated layer does not exist.

When As concentrated layer is present, get wet is resistant, why problems can be resolved in the viscosity increase when the solder paste is not clear, the viscosity increase is active agents contained in the Sn or Sn oxides and solder paste (flux) It is considered that this is caused by the formation of salt or the agglomeration of the solder material due to the reaction that occurs with various additives such as, and the presence of the As concentrated layer on the surface of the solder material causes the formation of a solder alloy. It is considered that the As-enriched layer is present between the fluxes, and the above-described reaction is less likely to occur. However, the mechanism does not depend on this.

In the present embodiment, the thickness of the As concentrated layer (converted to SiO ₂ ) is not limited, but is preferably 0.5 to 8.0 nm, more preferably 0.5 to 4.0 nm, and 0.5 to 2.0 nm. Is most preferred. Here, the thickness of the As concentrated layer means 2 × D1.
When the thickness of the As concentrated layer is in the above range, without adversely affecting the wettability, it is possible to suppress the viscosity increase over time when the source Rudapesuto sufficiently.

The solder material of the present embodiment, the content of the content and Bi of As relative to the total mass of the solder material is within the above range, by including the As concentration layer in the solder material, over time when the source Rudapesuto The increase in viscosity is suppressed and the wettability and reliability are excellent.

The method of manufacturing the solder material of the present embodiment is not limited, and it can be manufactured by melting and mixing the raw material metals.
There is no limitation on the method of forming the As concentrated layer in the solder material. An example of a method for forming the As concentrated layer is heating the solder material in an oxidizing atmosphere (air or oxygen atmosphere). The heating temperature is not limited, but may be, for example, 40 to 200 ° C, and may be 50 to 80 ° C. The heating time is not limited, and may be, for example, several minutes to several days, preferably several minutes to several hours. In order to form a sufficient amount of As concentrated layer, the heating time is preferably 10 minutes or longer, more preferably 20 minutes or longer.

In the present embodiment, the form of the solder material is not particularly limited, and may be a rod shape such as a bar solder, a wire shape, or a particle shape such as a solder ball or solder powder. Good.
When the solder material is in the form of particles, the fluidity of the solder material is improved.

  There is no limitation on the manufacturing method of the particulate solder material, and a known method such as a dropping method of dropping a molten solder material to obtain particles, a spraying method of centrifugal spraying, a method of crushing a bulk solder material, or the like is adopted. be able to. In the dropping method or the spraying method, the dropping or the spraying is preferably performed in an inert atmosphere or a solvent in order to form particles.

In addition, when the solder material is in the form of particles, if the size (particle size distribution) corresponding to the symbols 1 to 8 in the classification of the powder size in JIS Z 3284-1: 2014 (Table 2) is satisfied, fine parts are obtained. It is possible to solder to. The size of the particulate solder material is more preferably the size corresponding to the symbols 4 to 8, and more preferably the size corresponding to the symbols 5 to 8.
When the solder material is particulate, the sphericity is preferably 0.90 or more, more preferably 0.95 or more, and most preferably 0.99 or more.

  In the present embodiment, the usage form of the solder material is not particularly limited. For example, it may be mixed with oil or fat to form a flux cored solder, or when the solder material is in powder form, it may be used as a solder paste by mixing with a flux containing a rosin resin, an activator, a solvent, etc. Although it can be used as a ball, the solder material of the present embodiment is particularly suitable for use as a solder paste because it has a small increase in viscosity over time when used as a solder paste.

In this embodiment, the solder paste contains the solder powder and flux of this embodiment.
Here, the “flux” refers to the entire components other than the solder powder in the solder paste, and there is no limitation on the mass ratio of the solder powder and the flux (solder powder: flux), which should be set appropriately according to the application. You can

  In the present embodiment, the composition of the flux is not limited, and for example, a resin component; a solvent; an activator, a thixotropic agent, a pH adjusting agent, an antioxidant, a coloring agent, various additives such as a defoaming agent, and the like in any proportions. Can be included in. The resin, solvent and various additives are also not limited, and those generally used in solder paste can be used. Preferred 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 zirconium oxide powder. 0.05-20.0 mass% is preferable, as for content of the zirconium oxide powder with respect to the mass of the whole solder paste, 0.05-10.0 mass% is more preferable, and 0.1-3 mass% is the most preferable.
When the content of the zirconium oxide powder is within the above range, the activator contained in the flux preferentially reacts with the zirconium oxide powder, and the reaction with Sn or Sn oxide on the surface of the solder powder is less likely to occur. The effect of further suppressing the increase in viscosity due to the change is exhibited.

The upper limit of the particle size of the zirconium oxide powder added to the solder paste is not limited, but is preferably 5 μm or less. When the particle size is 5 μm or less, the printability of the paste can be maintained. The lower limit is also not particularly limited, but is preferably 0.5 μm or more. The above-mentioned particle size is a projection circle of a projection circle equivalent diameter of 0.1 μm or more when a SEM photograph of zirconium oxide powder is taken and the projection circle equivalent diameter is obtained by image analysis for each particle present in the visual field. Use the average value of equivalent diameters.
The shape of the zirconium oxide particles is not particularly limited, but if the zirconium oxide particles have a different shape, the contact area with the flux is large and the effect of increasing viscosity is suppressed. When it is spherical, good flowability is obtained, and thus excellent printability as a paste is obtained. The shape may be appropriately selected according to desired characteristics.

In the present embodiment, the solder paste can be manufactured by kneading the solder material (solder powder) of the present embodiment and the flux by a known method.
The solder paste according to the present embodiment can be used, for example, in a circuit board having a fine structure in an electronic device, and specifically, a printing method using a metal mask, an ejection method using a dispenser, or a transfer using a transfer pin. It can be applied to the soldered portion and reflowed by a method or the like.

In this embodiment, the solder material can be used as a joint (joint portion) for joining two or more various members. The joining member is not limited, and is also useful as a joint for electronic device members, for example.
In the present embodiment, the solder joint contains Sn or a Sn-based alloy, 40 to 250 mass ppm As, and 20 mass ppm to 3 mass% Bi, and includes an As concentrated layer in at least a part thereof. The solder joint of this embodiment can have the same composition and physical properties as the solder material of this embodiment described above, and can be formed using the solder material of this embodiment described above.
The content of content and Bi of As for the solder joint total mass is within the above range, when containing the As concentration layer in the solder joint, an excellent solder joint reliability.

  In the present embodiment, the solder joint is, for example, a solder ball made of the solder material of the present embodiment or the solder paste of the present embodiment, which is arranged or applied to a portion to be joined and heated, and which is common in the industry. Can be manufactured by a method.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the contents described in the examples.

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

(1) Evaluation of Presence / Absence of As Concentrated Layer The presence / absence of an As concentrated layer was evaluated as follows using depth direction analysis by XPS (X-ray Photoelectron Spectroscopy).
(Analysis conditions)
・ Analyzer: Micro area X-ray photoelectron spectroscopy analyzer (AXIS Nova manufactured by Kratos Analytical)
・ Analysis conditions: X-ray source AlKα ray, X-ray gun voltage 15 kV, X-ray gun current value 10 mA, analysis area 700 μm × 300 μm
・ Sputtering conditions: Ar species of ion, accelerating voltage of ² kV, sputtering rate of 0.5 nm / min (SiO ₂ conversion)
-Samples: Three samples were prepared by flatly laying a solder material (solder powders in Examples and Comparative Examples) on a stage on which a carbon tape was stuck without gaps, and used as samples. However, the size of the sample was 5.0 mm × 5.0 mm.
(Evaluation procedure)
XPS analysis chart for XPS analysis of Sn, O, and As atoms while ion sputtering is performed by selecting an area of 700 μm × 300 μm from a sample of 5.0 mm × 5.0 mm. Got One area was selected for each sample, and each of the three samples was analyzed once, for a total of three times.
Examples of charts obtained by XPS analysis are shown in FIGS. 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) in terms of SiO ₂ calculated from the sputtering time. In the XPS analysis chart, the vertical axis represents the detection intensity (cps), and the horizontal axis represents the sputtering time (min) or the SiO ₂ conversion depth calculated from the sputtering time using the sputter etching rate of the SiO ₂ standard sample. can be selected from any of the (nm), in Figures 1-3, the depth of the SiO ₂ in terms of the horizontal axis was calculated using the sputter etching rate of SiO ₂ standard sample from the sputtering time in the chart of XPS analysis (Nm).
Then, in the XPS analysis chart of each sample, the depth in terms of SiO _{2 at} which the detected intensity of O atom was maximum was defined as Do · max (nm) (see FIG. 2). Then, in a portion deeper than Do · max, the first SiO ₂ -converted depth at which the detected intensity of O atom is half the maximum detected intensity (intensity at Do · max) is D1 (nm). .
Then, in the XPS analysis chart of each sample, the integrated value of the detected intensity of As in the region from the outermost surface to the depth of 2 × D1 (region of SiO ₂ conversion depth of 0 to 2 × D1 (nm)) ( S1) and the integrated value of the detected intensity of As in the region from the depth 2 × D1 to a portion deeper by 2 × D1 (region where the SiO ₂ conversion depth is 2 × D1-4 × D1 (nm)) ( S2) (see FIG. 3) was obtained and the comparison was performed.
And it evaluated based on the following criteria.
・ S1> S2 in all three measurements
: As concentrated layer is formed (○)
・ S1> S2 when the number of measurements is 2 or less out of all 3 measurements
: As concentrated layer is not formed (x)

(2) Evaluation of suppression of thickening Each flux having the composition shown in Table 1 below was heated and stirred, and then cooled to prepare a flux. The prepared flux, and the solder powder of each of the examples and the comparative examples were kneaded so that the mass ratio of the flux and the solder powder (flux: solder powder) was 11:89 to produce a solder paste.

About the obtained solder paste, according to the method described in "4.2 Viscosity characteristic test" of JIS Z 3284-3, using a rotational viscometer (PCU-205, manufactured by Malcolm Co., Ltd.), rotation speed: 10 rpm, measurement The temperature was continuously measured at 25 ° C. for 12 hours. Then, the initial viscosity (viscosity after 30 minutes of stirring) 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 x 1.2: Good increase in viscosity with time is small (○)
Viscosity after 12 hours> Initial viscosity × 1.2: Large increase in viscosity over time and poor (×)

(3) Evaluation of solder wettability In the same manner as in “(2) Evaluation of suppression of thickening” described above, a solder paste was manufactured using the solder powders of Examples and Comparative Examples.
The obtained solder paste was printed on a Cu plate using a metal mask having an opening diameter of 6.5 mm, a numerical aperture of 4, and a mask thickness of 0.2 mm, and was heated in a reflow furnace under a N ₂ atmosphere at a temperature rising rate of 1 ° C. After heating from 25 ° C. to 260 ° C./sec, it was air-cooled to room temperature (25 ° C.) to form four solder bumps. The appearance of the obtained solder bumps was observed using an optical microscope (magnification: 100 times), and evaluation was performed based on the following criteria.
No solder particles that could not be completely melted were observed in all of the four solder bumps.
: Good solder wettability (○)
Solder particles that could not be completely melted were observed in one or more of the four solder bumps. : Poor solder wettability (×)

(4) Reliability Evaluation For each of the solder powders of Examples and Comparative Examples, using a differential scanning calorimeter (EXSTAR DSC7020, manufactured by SII Nano Technology Co., Ltd.), heating rate: 5 ° C./min (180 ° C.) To 250 ° C.), temperature drop rate: −3 ° C./min (250 ° C. to 150 ° C.), carrier gas: N ₂ , DSC measurement is performed, and liquidus temperature ( _TL ) and solidus temperature (T). _S ) was measured. Then, calculate the difference between the liquidus temperature (T _L) and the solidus temperature (T _S) and _{(ΔT = T L -T S)} , were evaluated based on the following criteria.
ΔT within 10 ° C: excellent reliability (○)
ΔT over 10 ° C: Poor reliability (x)
If the difference between the solder powder liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T S) is large, applying a solder paste containing the solder powder to the substrate of the electronic device After that, when solidifying, a structure having a high melting point is likely to be deposited on the surface of the solder powder. When a structure with a high melting point is deposited on the surface of the solder powder, then a structure with a low melting point is sequentially deposited toward the inside of the solder powder, and the structure of the solder powder is likely to be non-uniform, reducing the reliability such as cycleability. Cause.

(Examples A1 to A35, Comparative Examples A1 to A12)
Sn, As and Bi are weighed so that the contents of As and Bi are as shown in Table 2 below and Sn is the balance (the balance such that the total of Sn, As and Bi is 100% by mass). A powder (average particle diameter 21 μm, corresponding to 5 in JIS Z3284-1: 2014 powder size classification (Table 2)) was prepared by taking, melt-mixing, and centrifugally spraying in an Ar atmosphere. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples A1 to A6, the heat treatment was not applied, and the powder obtained by centrifugal spraying was used as the solder powder as it was.
In the table below, the content of As is mass ppm with respect to the mass of the entire solder material, and the content of Bi is mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.

(Examples B1 to B35, Comparative Examples B1 to B12)
As for Sn, As, Bi and Cu, the content of Cu is 0.7 mass%, the content of As and Bi is as shown in Table 3 below, and Sn is the balance (Sn, As, Bi and Cu). Powders (average particle diameter 21 μm, powder size classification 5) were prepared by weighing so that the total amount would be 100% by mass), melt mixing, and centrifugally spraying in an Ar atmosphere. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples B1 to B6, the heat treatment was not performed, and the powder obtained by centrifugal atomization was used as the solder powder as it was.
In the following table, the content of As is mass ppm with respect to the mass of the entire solder material, and the contents of Bi and Cu are mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.

(Examples C1 to C35, Comparative Examples C1 to C12)
For Sn, As, Bi, Ag and Cu, the Cu content is 0.5% by mass, the Ag content is 1.0% by mass, and the As and Bi contents are as shown in Table 4 below. Weigh so that Sn is the balance (remainder so that the total of Sn, As, Bi, Ag and Cu is 100% by mass), melt mix, and centrifuge in an Ar atmosphere to powder ( An average particle size of 21 μm and powder size classification 5) were prepared. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples C1 to C6, the heat treatment was not performed, and the powder obtained by centrifugal spraying was used as it was as the solder powder.
In the table below, the content of As is mass ppm with respect to the mass of the entire solder material, and the contents of Bi, Ag and Cu are mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.
The content of Sn, As, Bi, Ag and Cu of the solder powder obtained in Example C1 was analyzed by ICP-AES according to JIS Z 3910, and it could be confirmed that the content was the same as the charged amount. It was

(Examples D1 to D35, Comparative Examples D1 to D12)
Sn, As, Bi, Ag and Cu, the content of Cu is 0.5% by mass, the content of Ag is 2.0% by mass, and the contents of As and Bi are as shown in Table 5 below. Weigh so that Sn is the balance (remainder so that the total of Sn, As, Bi, Ag and Cu is 100% by mass), melt mix, and centrifuge in an Ar atmosphere to powder ( An average particle size of 21 μm and powder size classification 5) were prepared. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples D1 to D6, the heat treatment was not performed, and the powder obtained by centrifugal atomization was used as the solder powder as it was.
In the table below, the content of As is mass ppm with respect to the mass of the entire solder material, and the contents of Bi, Ag and Cu are mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.

(Examples E1 to E35, Comparative Examples E1 to E12)
Sn, As, Bi, Ag and Cu, the content of Cu is 0.5 mass%, the content of Ag is 3.0 mass%, the content of As and Bi are as shown in Table 6 below, Weigh so that Sn is the balance (remainder so that the total of Sn, As, Bi, Ag and Cu is 100% by mass), melt mix, and centrifuge in an Ar atmosphere to powder ( An average particle size of 21 μm and powder size classification 5) were prepared. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples E1 to E6, the heat treatment was not performed, and the powder obtained by centrifugal spraying was directly used as the solder powder.
In the table below, the content of As is mass ppm with respect to the mass of the entire solder material, and the contents of Bi, Ag and Cu are mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.

(Examples F1 to F35, Comparative examples F1 to F12)
Sn, As, Bi, Ag and Cu, the content of Cu is 0.5% by mass, the content of Ag is 3.5% by mass, the content of As and Bi are as shown in Table 7 below, Weigh so that Sn is the balance (remainder so that the total of Sn, As, Bi, Ag and Cu is 100% by mass), melt mix, and centrifuge in an Ar atmosphere to powder ( An average particle size of 21 μm and powder size classification 5) were prepared. The obtained powder was heated in air at 60 ° C. for 30 minutes using a drying device to obtain solder powders of Examples and Comparative Examples. However, in Comparative Examples F1 to F6, the heat treatment was not performed, and the powder obtained by centrifugal atomization was used as the solder powder as it was.
In the table below, the content of As is mass ppm with respect to the mass of the entire solder material, and the contents of Bi, Ag and Cu are mass% with respect to the mass of the entire solder material.
As Sn, a 3N material containing inevitable impurities was used.

  For each of the solder powders of Examples and Comparative Examples, (1) evaluation of presence / absence of As concentrated layer, (2) evaluation of thickening suppression, (3) evaluation of solder wettability, (4) evaluation of reliability The evaluation results are shown in Tables 2 to 7 below.

Since the solder material of the present invention is also available in various applications because of excellent reliability such as wettability and cycle characteristics I, among others, a small viscosity increase over time when a paste, a solder paste It can be suitably used as a solder material.

Claims (5)

4 0-250 ppm by weight of As, and comprises 20 wt ppm~3 wt% of Bi, and the balance of Sn, have a As-rich layer on the surface, the presence of As concentrated layer following criteria The solder alloy in which the As concentrated layer has a SiO ₂ converted thickness of 0.5 to 8.0 nm .
(Criteria)
Prepare a sample with a size of 5.0 mm × 5.0 mm (solder alloy (solder powder, solder balls, etc.) spread in a range of 5.0 mm × 5.0 mm without gaps), and select any 700 μm from it An area of × 300 μm is selected, and XPS analysis is performed with ion sputtering. One area is selected for each sample, and analysis is performed three times, once for each of the three samples. When the magnitude relationship between S1 and S2, which will be described later, is the same in all of the three analyzes (when the As concentrated layer is present on the surface side, S1> S2 in all three analyzes). , As is determined to be a concentrated layer.
Here, the definitions of S1, S2 and D1 are as follows.
S1: In the chart of XPS analysis performed on the above sample, the integrated value of the detected intensity of As in the region where the depth converted to SiO ₂ is 0 to 2 × D1 (nm)
S2: In the chart of XPS analysis performed on the above-mentioned sample, the integrated value of the detected intensity of As in the region where the SiO ₂ conversion depth is 2 × D1 to 4 × D1 (nm)
D1: In the chart of the XPS analysis performed on the above sample, the maximum detection intensity of O atoms was detected at a portion deeper than the depth of SiO ₂ (Do · max (nm)) where the maximum detection intensity of O atoms was maximum. Depth (nm) in terms of the first SiO _{2 that} is half the strength (strength at Do · max )
In the XPS analysis chart, when the detected intensity of O atom does not take the maximum value and D1 cannot be defined, it is determined that the As concentrated layer does not exist. 0-3.5 further comprising a mass% of Ag and / or 0 to 0.7 mass% of Cu, the solder alloy of claim 1. The form of the solder alloy is a powder, a solder alloy according to claim 1 or 2. A solder paste comprising the solder alloy according to claim 3 and a flux. A solder joint formed from the solder alloy according to claim 1 .