JP6674120B1 - Solder paste and flux for solder paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder paste which does not easily change with time, has excellent wettability, has high mechanical properties, and has good fluidity and shape retention. A solder paste containing a solder powder and a flux is adopted. Solder powder is at least one of As: 25 to 300 mass ppm, Pb: 0 mass ppm over 5100 mass ppm and Sb: 0 mass ppm over 3000 mass ppm and Bi: 0 mass ppm over 10,000 mass ppm. In addition, the balance includes a solder alloy having an alloy composition of Sn and satisfying the expressions (1) and (2). The flux contains rosin, a thixotropic agent, and a solvent. The thixotropic agent contains at least one selected from dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol. 275 ≦ 2As + Sb + Bi + Pb (1) 0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2) [Selection diagram] None

Description

  The present invention relates to a solder paste and a flux for a solder paste.

  In recent years, electronic devices having a solder joint such as a CPU (Central Processing Unit) have been required to be smaller and have higher performance. Accordingly, it is necessary to reduce the size of the printed circuit board and the electrodes of the electronic device. Since an electronic device is connected to a printed circuit board via an electrode, the size of the electrode is reduced and the size of a solder joint for connecting the two is also reduced.

In order to connect an electronic device and a printed board via such fine electrodes, a solder paste is generally used.
The solder paste is supplied on the electrodes of the printed circuit board by printing or the like. Solder paste printing consists of placing a metal mask with an opening on a printed circuit board, moving the squeegee while pressing it against the metal mask, and applying the solder paste to the electrodes on the printed circuit board from the metal mask opening. It is performed by Thereafter, the electronic component is placed on the solder paste printed on the printed circuit board and held by the solder paste until the soldering is completed.

  If, for example, several hours are required after the electronic component is placed on the printed circuit board until it is introduced into the reflow furnace, the solder paste may not be able to maintain the shape at the time of printing. In this case, it may cause a tilt of the electronic component or a bonding failure. In addition, when the solder paste is purchased, usually, the entire amount is not used up in one printing, so that the solder paste must maintain an appropriate viscosity at the beginning of manufacturing so as not to deteriorate the printing performance.

  However, in recent years, as the size of the electrode has been reduced, the printed area of the solder paste has also been reduced, so that the time until the purchased solder paste has been used has been prolonged. Solder paste is a mixture of solder powder and flux.If the storage period is long, the viscosity of the solder paste will increase depending on the storage conditions, and the printing performance at the time of purchase cannot be exhibited. Sometimes.

  Therefore, for example, Patent Document 1 includes Sn and one or more selected from the group consisting of Ag, Bi, Sb, Zn, In, and Cu in order to suppress a temporal change of the solder paste, Further, a solder alloy containing a predetermined amount of As is disclosed. The document shows that the viscosity after 2 weeks at 25 ° C. is less than 140% as compared with the viscosity at the beginning of production.

  On the other hand, the flux used for soldering chemically removes the metal oxides present on the metal surface of the solder and the joining object to be soldered, and enables the movement of metal elements at the boundary between the two. have. Therefore, by performing soldering using a flux, an intermetallic compound can be formed between the solder and the metal surface of the object to be joined, and a strong joint can be obtained.

  In a solder paste containing such soldering flux and solder powder, thixotropy is imparted by a thixo agent contained in the flux. The thixotropic agent builds a network in the flux and imparts thixotropic properties.

JP-A-2005-98052

  As described above, the invention described in Patent Document 1 is a solder alloy that can selectively contain six types of elements in addition to Sn and As. In addition, the document shows that when the As content is large, the meltability is poor.

  Here, the meltability evaluated in Patent Document 1 is considered to correspond to the wettability of the molten solder. The meltability disclosed in this document is evaluated by observing the appearance of the melt with a microscope and by the presence or absence of solder powder that cannot be melted completely. This is because if the wettability of the molten solder is high, the solder powder that cannot be melted hardly remains.

  Generally, in order to improve the wettability of molten solder, it is necessary to use a highly active flux. In the flux described in Patent Document 1, it is considered that a highly active flux may be used in order to suppress the deterioration of wettability due to As. However, when a highly active flux is used, the rate of increase in the viscosity of the flux increases. Also, in view of the description of Patent Document 1, it is necessary to increase the As content in order to suppress the increase in the rate of increase in viscosity. In order for the solder paste described in Patent Document 1 to exhibit a lower viscosity increase rate and excellent wettability, it is necessary to keep increasing the flux activation power and As content, which causes a vicious cycle.

  In recent years, solder pastes have been required to maintain stable performance for a long period of time irrespective of use environment and storage environment, and further higher wettability has been required due to miniaturization of solder joints. When trying to respond to recent demands using the solder paste described in Patent Document 1, a vicious cycle is inevitable as described above.

  Furthermore, in order to join fine electrodes, it is necessary to improve the mechanical properties and the like of the solder joint. If the content of some elements increases, the liquidus temperature increases, the liquidus temperature and the solidus temperature increase, and segregation occurs during solidification to form a non-uniform alloy structure. When the solder alloy has such an alloy structure, mechanical properties such as tensile strength are inferior, and the solder alloy is easily broken by external stress. This problem has become remarkable with recent miniaturization of electrodes.

  The supply of the solder paste onto the electrodes of the printed circuit board is usually performed by dispenser discharge or screen printing. For this reason, the solder paste is required to have printability such as dischargeability and plate skipping, and further needs to maintain its shape after being supplied. The flow characteristics (thixotropic property) of the solder paste, which has both fluidity (low viscosity) at the time of ejection and printing and shape retention (high viscosity) after supply, are the fine characteristics in the surface mounting of substrates, which have been increasing in density in recent years. This is an important factor in pitch printing.

  The present invention has been made in order to solve the above-mentioned problems, and is unlikely to occur with time such as viscosity increase, has excellent wettability, has high mechanical properties, and has good fluidity and shape retention. It is intended to provide a simple solder paste.

  When the suppression of the change over time of the solder paste and the excellent wettability are simultaneously improved, it is necessary to use a flux having a high activity and avoid a vicious cycle due to an increase in the As content. The present inventors have focused on the alloy composition of the solder powder, and have conducted intensive studies in order to achieve both suppression of the change over time of the solder paste and excellent wettability.

  First, the present inventors studied a solder powder containing As as a basic composition based on Sn, SnCu, and SnAgCu solder alloys conventionally used as solder alloys. Then, when this solder powder was used, attention was paid to the reason for suppressing the temporal change of the solder paste, and the As content was examined.

  It is considered that the reason why the viscosity of the solder paste increases with time is that the solder powder reacts with the flux. When the results of Example 4 and Comparative Example 2 in Table 1 of Patent Document 1 are compared, it is found that the case where the As content exceeds 100 ppm by mass has a lower viscosity increase rate. In view of these, it was considered that the As content may be further increased when attention is paid to the effect of suppressing the temporal change of the solder paste (hereinafter, referred to as the “viscosity suppressing effect” as appropriate). When the As content was increased, the effect of suppressing thickening slightly increased with the As content, but it was confirmed that when the As content was too large, the wettability of the solder alloy deteriorated.

  Then, the present inventors came to the conclusion that it was necessary to add an element exhibiting a thickening suppressing effect in addition to As, and examined various elements. As a result, Sb, Bi and Pb were found to be As Obtained the same effect as described above. The reason for this is not clear, but is presumed as follows.

  Since the effect of suppressing thickening is exhibited by suppressing the reaction with the flux, an element having a low reactivity with the flux includes an element having a low ionization tendency. Generally, the ionization of an alloy is considered based on the ionization tendency as an alloy composition, that is, the standard electrode potential. For example, a SnAg alloy containing Ag which is noble to Sn is less likely to ionize than Sn. For this reason, an alloy containing an element nobler than Sn is less likely to be ionized, and is presumed to have a high effect of suppressing the viscosity increase of the solder paste.

  Here, in Patent Document 1, Bi, Sb, Zn, and In are listed as equivalent elements in addition to Sn, Ag, and Cu. However, In and Zn have a lower ionization tendency than Sn. Element. In other words, Patent Literature 1 describes that the effect of suppressing thickening can be obtained even when an element more noble than Sn is added. For this reason, it is considered that a solder alloy containing an element selected according to the ionization tendency can obtain a thickening suppression effect equal to or greater than that of the solder alloy described in Patent Document 1. Further, as described above, when the As content increases, the wettability deteriorates.

  The present inventors have studied in detail Bi and Pb found as a thickening suppressing effect. Since Bi and Pb lower the liquidus temperature of the solder alloy, when the heating temperature of the solder alloy is constant, the wettability of the solder alloy is improved. However, the solidus temperature is significantly reduced depending on the content thereof, so that ΔT, which is the temperature difference between the liquidus temperature and the solidus temperature, becomes too wide. If ΔT is too wide, segregation occurs at the time of solidification, leading to a decrease in mechanical properties such as mechanical strength. Since the phenomenon that ΔT is widespread appears remarkably when Bi and Pb are added simultaneously, it has also been found that strict control is necessary.

  In addition, the present inventors reviewed the Bi content and the Pb content in order to improve the wettability of the solder alloy. However, when the content of these elements increased, ΔT became wider. Therefore, the present inventors have selected Sb as an element whose ionization tendency is noble with respect to Sn and also as an element for improving the wettability of a solder alloy, and set an allowable range of the Sb content. The relationship regarding the content of each of As, Bi, Pb and Sb including Sb was examined in detail. As a result, by chance, when the content of these elements satisfies the predetermined relational expression, it is found that there is no practical problem in all of the excellent thickening suppression effect, wettability, and narrowing of ΔT. Was.

  Further, a flux containing a specific sorbitol-based thixotropic agent can exhibit sufficient thixotropic properties.

The present invention obtained based on these findings is as follows.
[1] A solder paste containing a solder powder and a flux, wherein the solder powder contains As: 25 to 300 mass ppm, Pb: more than 0 mass ppm, 5100 mass ppm or less, and Sb: 0 mass ppm. Over 3000 mass ppm, and Bi: at least one of over 0 mass ppm to 10,000 mass ppm, and a balance having an alloy composition consisting of Sn, including a solder alloy satisfying the following formulas (1) and (2); The flux includes a rosin, a thixotropic agent, and a solvent, wherein the thixotropic agent is at least one sorbitol-based thixotropic agent selected from the group consisting of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol. Solder paste containing 0.2% by mass or more and 5.0% by mass or less.
275 ≦ 2As + Sb + Bi + Pb (1)
0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formulas (1) and (2), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition.

[2] The solder paste according to [1], wherein the alloy composition satisfies the following formula (1a).
275 ≦ 2As + Sb + Bi + Pb ≦ 25200 (1a)
In the above formula (1a), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

[3] The solder paste according to [1], wherein the alloy composition satisfies the following formula (1b).
275 ≦ 2As + Sb + Bi + Pb ≦ 5300 (1b)
In the above formula (1b), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

[4] The solder paste according to any one of [1] to [3], wherein the alloy composition satisfies the following formula (2a).
0.31 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2a)
In the above formula (2a), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

[5] The alloy composition according to any one of [1] to [4], wherein the alloy composition contains at least one selected from the group consisting of Ag: 0 to 4% by mass and Cu: 0 to 0.9% by mass. The solder paste according to claim 1.

[6] The thixotropic agent is at least one sorbitol selected from the group consisting of (D-) sorbitol, monobenzylidene (-D-) sorbitol, and mono (4-methylbenzylidene)-(D-) sorbitol. The solder paste according to any one of the above [1] to [5], containing a system additive.

[7] against the sorbitol-based thixotropic agent, said sorbitol ratio of additive (weight ratio) is not more than 1.50% of 0.03% or more, the solder paste according to the above [6].

[8] The solder paste according to any one of [1] to [7], further including 0.5 to 15.0% by mass of at least one selected from the group consisting of an ester compound and an amide compound. .

[9] The solder paste according to any one of [1] to [8], wherein the solvent is at least one selected from the group consisting of an aliphatic glycol-based solvent and an aromatic glycol-based solvent.

[10] The method according to any one of [1] to [9], wherein the rosin contains 15% by mass or more and 70% by mass or less and the organic acid contains 0% by mass or more and 2.0% by mass or less. Solder paste.

[11] Further, 0% to 2% by mass of an amine, 0% to 8.0% by mass of an organic halogen compound, 0% to 5.0% by mass of an amine hydrohalide, and The solder paste according to any one of the above [1] to [10], comprising an antioxidant in an amount of 0% by mass to 8% by mass.

[12] A flux used for a solder paste, wherein the flux contains rosin, a thixotropic agent, and a solvent, and the thixotropic agent is composed of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol. A sorbitol-based thixotropic agent, which is at least one selected from the group, in an amount of 0.2% by mass or more and 5.0% by mass or less, and the solder paste contains 25% to 300% by mass of As, and 5100% by mass of Pb exceeding 0% by mass. Sb: at least one of Sb: more than 0 mass ppm to 3,000 mass ppm and Bi: more than 0 mass ppm to 10,000 mass ppm, and the balance has an alloy composition consisting of Sn, and the following formula (1) and (2) Flux for solder paste containing solder powder containing solder alloy that satisfies the formula.
275 ≦ 2As + Sb + Bi + Pb (1)
0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formulas (1) and (2), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition.

According to the present invention, it is possible to provide a solder paste which hardly undergoes a change over time such as an increase in viscosity, has excellent wettability, has high mechanical properties, and has good fluidity and shape retention.
Further, according to the present invention, it is possible to provide a flux for a solder paste that can impart sufficient thixotropic properties, preferably suppresses crystal precipitation, and hardly causes lumps.

The present invention is described in more detail below.
In this specification, “ppm” regarding the solder alloy composition is “mass ppm” unless otherwise specified. “%” Is “% by mass” unless otherwise specified.

<Solder paste>
The solder paste of the present embodiment contains a specific solder powder and a specific flux.

≪Solder powder≫
The solder powder used in the solder paste of the present embodiment includes As: 25 to 300 mass ppm, Pb: more than 0 mass ppm to 5100 mass ppm, and Sb: more than 0 mass ppm to 3000 mass ppm, and Bi: 0 mass ppm. At least one of not more than 10,000 mass ppm and a solder alloy having an alloy composition consisting of Sn in the balance and satisfying the following formulas (1) and (2) are included.
275 ≦ 2As + Sb + Bi + Pb (1)
0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formulas (1) and (2), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition.

1. Alloy composition (1) As: 25 to 300 mass ppm
As is an element capable of suppressing a change with time in the viscosity of the solder paste. It is presumed that As has low reactivity with flux and is an element noble to Sn, so that it can exert a thickening suppressing effect. When As is less than 25 ppm by mass, the effect of suppressing thickening cannot be sufficiently exhibited. The lower limit of the As content is 25 ppm by mass or more, preferably 50 ppm by mass or more, and more preferably 100 ppm by mass or more. On the other hand, if the content of As is too large, the wettability of the solder alloy deteriorates. The upper limit of the As content is 300 ppm by mass or less, preferably 250 ppm by mass or less, and more preferably 200 ppm by mass or less.

(2) Pb: at least one of 0 mass ppm to 5100 mass ppm or less, and Sb: at least one mass of more than 0 mass ppm to 3000 mass ppm and Bi: more than 0 mass ppm to 10000 mass ppm Sb has low reactivity with flux. It is an element that exhibits a thickening suppressing effect. When the solder alloy according to the present invention contains Sb, the lower limit of the Sb content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and still more preferably 100 mass ppm. ppm or more, particularly preferably 300 ppm by mass or more. On the other hand, if the Sb content is too large, the wettability deteriorates, so it is necessary to make the Sb content appropriate. The upper limit of the Sb content is 3000 ppm by mass or less, preferably 1150 ppm by mass or less, more preferably 500 ppm by mass or less.

  Bi and Pb, like Sb, are elements having low reactivity with flux and exhibiting a thickening suppressing effect. Further, Bi and Pb are elements that can lower the liquidus temperature of the solder alloy and reduce the viscosity of the molten solder, thereby suppressing the deterioration of wettability due to As.

  If at least one element of Pb, Sb, and Bi is present, deterioration of wettability by As can be suppressed. When the solder alloy according to the present invention contains Bi, the lower limit of the Bi content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and still more preferably 75 mass ppm. ppm or more, particularly preferably 100 ppm or more, and most preferably 250 ppm or more. The lower limit of the Pb content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, still more preferably 75 mass ppm or more, and particularly preferably 100 mass ppm or more. And most preferably at least 250 ppm by mass.

  On the other hand, if the content of these elements is too large, the solidus temperature is remarkably lowered, so that ΔT, which is the temperature difference between the liquidus temperature and the solidus temperature, becomes too wide. If ΔT is too wide, a liquid phase Bi or Pb is concentrated in the solidification process of the molten solder because a high melting point crystalline phase having a low content of Bi or Pb is deposited. Thereafter, when the temperature of the molten solder further decreases, a low melting point crystal phase having a high concentration of Bi or Pb segregates. For this reason, the mechanical strength and the like of the solder alloy are deteriorated, and the reliability is deteriorated. In particular, since the crystal phase having a high Bi concentration is hard and brittle, the segregation in the solder alloy significantly lowers the reliability.

  From such a viewpoint, when the solder alloy according to the present invention contains Bi, the upper limit of the Bi content is 10,000 mass ppm or less, preferably 1,000 mass ppm or less, more preferably 600 mass ppm or less. , More preferably 500 ppm by mass or less. The upper limit of the Pb content is 5100 mass ppm or less, preferably 5000 mass ppm or less, more preferably 1000 mass ppm or less, still more preferably 850 mass ppm or less, and particularly preferably 500 mass ppm or less. is there.

(3) Formula (1) The solder alloy according to the present invention needs to satisfy the following formula (1).

275 ≦ 2As + Sb + Bi + Pb (1)
In the above formula (1), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

  As, Sb, Bi, and Pb are all elements that exhibit a thickening inhibiting effect, and their total needs to be 275 mass ppm or more. In the formula (1), the reason why the As content is doubled is that As has a higher effect of suppressing thickening than Sb, Bi, or Pb.

  If the value of the expression (1) is less than 275, the effect of suppressing thickening is not sufficiently exhibited. The lower limit of the formula (1) is 275 or more, preferably 350 or more, and more preferably 1200 or more. On the other hand, the upper limit of the formula (1) is not particularly limited in terms of the effect of suppressing thickening, but is preferably 25200 or less, more preferably 10200 or less, from the viewpoint of setting ΔT in a suitable range. , More preferably 5300 or less, particularly preferably 3800 or less.

  The following formulas (1a) and (1b) are those in which the upper and lower limits are appropriately selected from the above preferred embodiments.

275 ≦ 2As + Sb + Bi + Pb ≦ 25200 (1a)
275 ≦ 2As + Sb + Bi + Pb ≦ 5300 (1b)
In the above formulas (1a) and (1b), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

(4) Formula (2) The solder alloy according to the present invention needs to satisfy the following formula (2).

0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formula (2), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

  When the content of As and Sb is large, the wettability of the solder alloy is deteriorated. On the other hand, Bi and Pb suppress the deterioration of wettability due to the inclusion of As. However, if the content is too large, ΔT increases, so strict management is required. In particular, in an alloy composition containing Bi and Pb simultaneously, ΔT tends to increase. In view of these, if the content of Bi and Pb is increased to improve the wettability excessively, ΔT will be widened. On the other hand, when the content of As or Sb is increased to improve the effect of suppressing thickening, wettability deteriorates. Therefore, in the present invention, the group is divided into As and Sb groups and Bi and Pb groups, and when the total amount of both groups is within an appropriate predetermined range, the thickening suppression effect, the narrowing of ΔT, and the wettability Are all satisfied at the same time.

  If the expression (2) is less than 0.01, the total content of Bi and Pb becomes relatively larger than the total content of As and Pb, so that ΔT is widened. The lower limit of the formula (2) is 0.01 or more, preferably 0.02 or more, more preferably 0.41 or more, further preferably 0.90 or more, and particularly preferably 1.00 or more. And most preferably 1.40 or more. On the other hand, if the expression (2) exceeds 10.00, the total content of As and Sb becomes relatively larger than the total content of Bi and Pb, so that the wettability deteriorates. The upper limit of the formula (2) is 10.00 or less, preferably 5.33 or less, more preferably 4.50 or less, still more preferably 2.67 or less, and still more preferably 2.50. And particularly preferably 2.30 or less.

Note that the denominator of the expression (2) is “Bi + Pb”, and the expression (2) is not satisfied unless these are included. That is, the solder alloy according to the present invention always contains at least one of Bi and Pb. As described above, the alloy composition containing neither Bi nor Pb has poor wettability.
The following formula (2a) is obtained by appropriately selecting the upper and lower limits from the above preferred embodiments.

0.31 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2a)
In the above formula (2a), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.

(5) Ag: 0 to 4 wt% and Cu: at least one of Ag 0 to 0.9% by weight, with optional elements which can improve the reliability of the solder to form a _Ag 3 Sn in the crystal interface alloy is there. Ag is an element having a higher ionization tendency than Sn, and promotes the effect of suppressing thickening of these elements by coexisting with As, Pb and Bi. The Ag content is preferably 0 to 4% by mass, more preferably 0.5 to 3.5% by mass, and still more preferably 1.0 to 3.0% by mass.

  Cu is an optional element that can improve the bonding strength of the solder joint. Further, Cu is an element having a higher ionization tendency than Sn and coexists with As, Pb, and Bi to promote the effect of suppressing thickening of these elements. The Cu content is preferably from 0 to 0.9% by mass, more preferably from 0.1 to 0.8% by mass, and still more preferably from 0.2 to 0.7% by mass.

(6) Remainder: Sn
The balance of the solder alloy in the present embodiment is Sn. Inevitable impurities may be contained in addition to the aforementioned elements. Even if unavoidable impurities are contained, the effects described above are not affected. Further, as described later, even if an element which is not contained in the present invention is contained as an unavoidable impurity, the above-mentioned effect is not affected. If the content of In is too large, ΔT is widened. Therefore, if the content is 1000 ppm or less, the above-mentioned effect is not affected.

2. Solder Powder The solder powder in the present embodiment preferably satisfies a size (particle size distribution) satisfying the symbols 1 to 8 in the powder size classification (Table 2) in JIS Z 3284-1: 2014. More preferably, it is a size (particle size distribution) that satisfies the symbols 4 to 8, and still more preferably a size (particle size distribution) that satisfies the symbols 5 to 8. When the particle size satisfies this condition, the surface area of the powder is not too large and the increase in viscosity is suppressed, and the aggregation of the fine powder is suppressed and the increase in viscosity may be suppressed. For this reason, soldering to finer components becomes possible.

≪Flux≫
The flux used for the solder paste of the present embodiment contains rosin, a thixotropic agent, and a solvent.

  Examples of the rosin include natural rosin, derivatives obtained from the natural rosin, and the like. Examples of the natural rosin include gum rosin, wood rosin, and tall oil rosin. Examples of the derivative include purified rosin and modified rosin. Examples of the modified rosin include hydrogenated rosin, polymerized rosin, disproportionated rosin, acid-modified rosin, rosin ester, phenol-modified rosin and α, β unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.) ), And purified, hydrogenated and disproportionated products of the polymerized rosin, and purified, hydrogenated and disproportionated products of the α, β unsaturated carboxylic acid-modified product, and one or two of these. The above can be used.

  The flux of the present embodiment preferably contains rosin in a range of 15% to 70% by mass, and more preferably 35% to 60% by mass of rosin.

The thixotropic agent used in the present embodiment includes a sorbitol-based thixotropic agent that is at least one selected from the group consisting of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol.
The content of the sorbitol-based thixotropic agent is 0.2% by mass or more and 5.0% by mass or less, preferably 0.5% by mass or more and 3.5% by mass or less based on the total amount of the entire flux.

As the thixotropic agent used in the present embodiment, a thixotropic agent other than the sorbitol-based thixotropic agent may be used in combination.
Examples of the thixotropic agent other than the sorbitol-based thixotropic agent include sorbitol-based additives and other thixotropic agents.

Examples of the sorbitol-based additive include (D-) sorbitol, monobenzylidene (-D-) sorbitol, mono (4-methylbenzylidene)-(D-) sorbitol, and the like.
The content of the sorbitol-based additive is preferably more than 0% by mass and 0.035% by mass or less, more preferably 0.00025% by mass or more and 0.035% by mass or less based on the total amount of the entire flux.

Other thixotropic agents include at least one selected from the group consisting of ester compounds and amide compounds.
Other ester compounds that are thixotropic agents include, for example, hardened castor oil.

Other amide compounds that are thixotropic agents include, for example,
Lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, p-toluenemethaneamide, aromatic Monoamides such as amide, hexamethylenehydroxystearic acid amide, substituted amide, methylolstearic acid amide, methylolamide, fatty acid ester amide;
Methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebishydroxy fatty acid (C6-24 carbon number of fatty acid) amide, ethylenebishydroxystearic acid amide, saturated fatty acid bisamide, methylenebisoleic acid amide, unsaturated fatty acid bisamide, m Bisamides such as xylylene bisstearic acid amide and aromatic bisamide;
Polyamides such as saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, 1,2,3-propanetricarboxylic acid tris (2-methylcyclohexylamide), cyclic amide oligomer and acyclic amide oligomer are exemplified.

  The cyclic amide oligomer includes an amide oligomer in which a dicarboxylic acid and a diamine are cyclically polycondensed, an amide oligomer in which a tricarboxylic acid and a diamine are cyclically polycondensed, an amide oligomer in which a dicarboxylic acid and a triamine are cyclically polycondensed, and a tricarboxylic acid. Oligomer obtained by cyclic polycondensation of diamine and triamine, amide oligomer obtained by cyclic polycondensation of dicarboxylic acid and tricarboxylic acid and diamine, amide oligomer obtained by cyclic polycondensation of dicarboxylic acid and tricarboxylic acid and triamine, dicarboxylic acid and diamine Amide oligomers obtained by cyclic polycondensation of triamine and triamine, amide oligomers obtained by cyclic polycondensation of tricarboxylic acid and diamine and triamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid and tricarboxylic acid with diamine and triamine Goma, and the like.

  When the non-cyclic amide oligomer is an amide oligomer in which a monocarboxylic acid and a diamine and / or a triamine are non-cyclically polycondensed, the amide in which a dicarboxylic acid and / or a tricarboxylic acid and a monoamine are non-cyclically polycondensed is used. For example, it may be an oligomer. When the amide oligomer contains a monocarboxylic acid or a monoamine, the monocarboxylic acid or the monoamine functions as terminal molecules and becomes an acyclic amide oligomer having a reduced molecular weight. In addition, when the acyclic amide oligomer is an amide compound in which a dicarboxylic acid and / or a tricarboxylic acid and a diamine and / or a triamine are acyclicly polycondensed, the acyclic amide oligomer becomes a noncyclic high molecular amide polymer. Furthermore, the acyclic amide oligomer also includes an amide oligomer in which a monocarboxylic acid and a monoamine are acyclicly condensed.

Other thixo agents are preferably at least one selected from the group consisting of ester compounds and amide compounds. Among these, at least one selected from the group consisting of castor hardened oil and ethylene bishydroxy fatty acid (carbon number of fatty acid C6-24) amide is more preferable, and at least one selected from the group consisting of castor hardened oil and ethylene bishydroxystearic amide. At least one is more preferred.
The content of such other thixotropic agents is preferably from 0.5 to 15.0% by mass, more preferably from 1% by mass to 10% by mass, based on the total amount of the entire flux.

  The flux of the present embodiment preferably contains a sorbitol-based thixotropic agent and another thixotropic agent in a total amount of 2% by mass or more and 15% by mass or less, more preferably 2.5% by mass or more and 11.5% by mass or less. preferable.

  The flux of the present embodiment preferably contains the total amount of the thixotropic agent in the range of 2% by mass to 15% by mass, more preferably 2.5% by mass to 11.5% by mass.

  The thixotropic agent of the flux of the present embodiment is obtained by combining a sorbitol-based thixotropic agent, which is at least one selected from the group consisting of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol, with another thixotropic agent. Preferably, it is used. Thereby, in addition to imparting thixotropic properties, precipitation of crystals and generation of lumps in the flux and the solder paste using the flux are easily suppressed.

The thixotropic agent for the flux of the present embodiment preferably uses the sorbitol-based thixotropic agent and the sorbitol-based additive in combination.
More preferred thixotropic agents are the sorbitol-based thixotropic agents and at least one selected from the group consisting of (D-) sorbitol, monobenzylidene (-D-) sorbitol, and mono (4-methylbenzylidene)-(D-) sorbitol. A sorbitol-based additive.

The ratio (mass ratio) of the sorbitol-based additive to the sorbitol-based thixotropic agent is preferably 0.03 % to 1.50 %, and more preferably 0.05 % to 1.00 %. More preferred.

  In the thixotropic agent for the flux of the present embodiment, it is preferable to use the sorbitol-based thixotropic agent, the sorbitol-based additive, and the other thixotropic agents in combination.

Examples of the solvent include water, alcohol solvents, glycol ether solvents, terpineols, and the like.
Examples of alcohol solvents include isopropyl alcohol, 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-tris (hydroxymethyl) Ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2′-oxybis (methylene) bis (2-ethyl-1,3-propanediol), 2,2-bis (hydroxymethyl) -1,3-propanediol, 1,2,6-trihydroxyhexane, bis [2,2,2-tris (hydroxymethyl) ethyl] ether 1,1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the like.
As glycol ether solvents,
Hexyl glycol, hexyl diglycol, 2-ethylhexyl glycol, 2-ethylhexyl diglycol, dimethyl triglycol, dibutyl diglycol, diethylene glycol mono-2-ethylhexyl ether, 2-methylpentane-2,4-diol, diethylene glycol monohexyl ether, Aliphatic glycol ether solvents such as diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether;
Aromatic glycol ether solvents such as phenyl glycol, phenyl diglycol, benzyl glycol, benzyl diglycol, ethylene glycol monophenyl ether;
And the like.

One or more solvents can be used.
The solvent is preferably a glycol ether-based solvent, and is preferably selected from the group consisting of an aliphatic glycol-based solvent and an aromatic glycol-based solvent, since precipitation of crystals in a flux and a solder paste using the same and generation of lumps are easily suppressed. At least one of the above is more preferable.

  The flux of the present embodiment may contain components other than the rosin, the thixotropic agent, and the solvent, and examples thereof include an organic acid, an amine, a halogen-based activator, and an antioxidant.

  Organic acids include glutaric acid, adipic acid, azelaic acid, eicosantioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, and thioglycol. Acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris (2-carboxyethyl) isocyanurate Glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid , 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, Gore acid, p- anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, and linolenic acid.

  Examples of the organic acid include dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product obtained by adding hydrogen to dimer acid, and hydrogenated trimer acid which is a hydrogenated product obtained by adding hydrogen to trimer acid.

  For example, dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid, trimer acid which is a reaction product of acrylic acid, and methacrylic acid Dimer acid, which is a reactant of methacrylic acid, dimer acid which is a reactant of acrylic acid and methacrylic acid, trimer acid which is a reactant of acrylic acid and methacrylic acid, and a reactant of oleic acid Certain dimer acids, trimer acid which is a reaction product of oleic acid, dimer acid which is a reaction product of linoleic acid, trimer acid which is a reaction product of linoleic acid, dimer acid which is a reaction product of linolenic acid, and a reaction product of linolenic acid Certain trimer acids, dimer acid which is a reaction product of acrylic acid and oleic acid, trimer acid which is a reaction product of acrylic acid and oleic acid, Dimer acid which is a reaction product of lylic acid and linoleic acid, trimer acid which is a reaction product of acrylic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid and linolenic acid, and a trimer which is a reaction product of acrylic acid and linolenic acid Acid, dimer acid which is a reaction product of methacrylic acid and oleic acid, trimer acid which is a reaction product of methacrylic acid and oleic acid, dimer acid which is a reaction product of methacrylic acid and linoleic acid, a reaction product of methacrylic acid and linoleic acid Certain trimer acid, dimer acid which is a reaction product of methacrylic acid and linolenic acid, trimer acid which is a reaction product of methacrylic acid and linolenic acid, dimer acid which is a reaction product of oleic acid and linolenic acid, reaction of oleic acid and linolenic acid Dimer acid, a reaction product of linoleic acid and linolenic acid, and a reaction product of linoleic acid and linolenic acid Trimer acid that, hydrogenated dimer acid which is a hydrogenation product of the dimer acid as described above, hydrogenated trimer acid, and the like are hydrogenated products of the trimer acid described above.

One type of organic acid may be used alone, or two or more types may be used in combination.
The flux of the present embodiment preferably contains 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 2.0% by mass or less of the organic acid.

  Examples of the amine include monoethanolamine, diphenylguanidine, ditolylguanidine, ethylamine, triethylamine, cyclohexylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 1,2-dimethyl. Imidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methyl Imidazole, 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′-undecylimidazolyl- (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-phenylimidazole 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-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octyl Benzimidazole, 2-pentylbenzimidazole, 2- (1-ethylpentyl) benzimidazole, 2-nonylbenzimidazole, 2- (4-thiazolyl) benzimidazole, benzimidazole, 2- (2′-hydroxy-5′-) Methylphenyl) benzotriazole 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) Benzotriazole, 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, 2,2′-methylenebis [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] benzotriazole, carboxybenzotriazole, 1- [N, N-bis (2-ethyl Xyl) aminomethyl] methylbenzotriazole, 2,2 ′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bisethanol, 1- (1 ′, 2′-dicarboxyethyl) benzotriazole , 1- (2,3-dicarboxypropyl) benzotriazole, 1-[(2-ethylhexylamino) methyl] benzotriazole, 2,6-bis [(1H-benzotriazol-1-yl) methyl] -4- Examples thereof include methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, and triazole.

The amines may be used alone or as a mixture of two or more.
The flux of the present embodiment preferably contains 0% by mass or more and 5% by mass or less, more preferably 0% by mass or more and 2.0% by mass or less.

The flux of the present embodiment may contain a halogen-based activator.
Examples of the halogen-based activator include amine hydrohalides, organic halogen compounds, and the like.

Amine hydrohalide is a compound obtained by reacting an amine with hydrogen halide.
As the amine in the amine hydrohalide, the above-mentioned amines can be used, and examples thereof include ethylamine, cyclohexylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylguanidine, methylimidazole, and 2-ethyl-4-methylimidazole. Can be Examples of the hydrogen halide include hydrides of chlorine, bromine, iodine, and fluorine (hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen fluoride). Further, a borofluoride may be contained in place of the amine hydrohalide or in combination with the amine hydrohalide, and examples of the borofluoride include borofluoric acid.
Examples of the amine hydrohalide include aniline hydrogen chloride, cyclohexylamine hydrogen chloride, aniline hydrogen bromide, diphenylguanidine hydrogen bromide, ditolylguanidine hydrogen bromide, and ethylamine hydrogen bromide.

  Examples of the organic halogen compound include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate hexabromide, 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-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, tris (2,3-dibromopropyl) isocyanurate, Chlorendic anhydride and the like can be mentioned.

  The flux of the present embodiment preferably contains an organic halogen compound in an amount of 0% by mass to 8.0% by mass, more preferably 0% by mass to 5.0% by mass; It is preferably contained in an amount of 0% by mass or more and 5.0% by mass or less, more preferably 0% by mass or more and 3.0% by mass or less.

Examples of the antioxidant include 2,2′-methylenebis [6- (1-methylcyclohexyl) -p-cresol], a hindered phenol-based antioxidant, and the like.
The flux of the present embodiment preferably contains 0% by mass to 8% by mass of the antioxidant, more preferably 0% by mass to 5.0% by mass.

The flux of the present embodiment may further contain a surfactant.
Examples of the surfactant include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, polyoxyalkylene alkylamine, and polyoxyalkylene alkylamide.

Flux content:
The content of the flux is preferably 5 to 95% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.
When the content of the flux in the solder paste is within this range, the effect of suppressing viscosity increase caused by the solder powder is sufficiently exhibited. In addition, thixotropic properties are sufficiently imparted, and the fluidity and shape retention of the paste are easily enhanced.

  It is preferable that the solder paste of the present embodiment further contains zirconium oxide powder. By containing zirconium oxide, it is possible to suppress an increase in the viscosity of the paste due to aging. This is presumed to be due to the inclusion of zirconium oxide to maintain the oxide film thickness on the surface of the solder powder before it was introduced into the flux. Details are unknown, but are presumed as follows. Normally, since the active component of the flux has a slight activity even at room temperature, the surface oxide film of the solder powder is thinned by reduction, which causes the powder to agglomerate. Therefore, it is presumed that by adding zirconium oxide powder to the solder paste, the active component of the flux reacts preferentially with the zirconium oxide powder, and is maintained to such an extent that the oxide film on the surface of the solder powder does not aggregate.

  In order to sufficiently exhibit such effects, the content of the zirconium oxide powder in the solder paste is preferably 0.05 to 20.0% by mass based on the total mass of the solder paste. When the content is 0.05% by mass or more, the above function and effect can be exhibited, and when the content is 20.0% by mass or less, the content of the metal powder can be secured, and the effect of preventing thickening is exhibited. Can be. The content of the zirconium oxide powder is more preferably 0.05 to 10.0% by mass, and still more preferably 0.1 to 3% by mass.

The particle diameter of the zirconium oxide powder in the solder paste 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 of the particle size is not particularly limited, but may be 0.5 μm or more.
The particle diameter of the zirconium oxide powder is determined by taking an SEM photograph of the zirconium oxide powder, obtaining an equivalent projected circle diameter by image analysis for each powder having a diameter of 0.1 μm or more, and setting the average value thereof.

  The shape of the zirconium oxide is not particularly limited, but a different shape has a large contact area with the flux and has an effect of suppressing thickening. When the shape is spherical, good printability as a paste is obtained because good fluidity is obtained. What is necessary is just to select a shape suitably according to a desired characteristic.

Manufacturing method of solder paste:
The solder paste of the present embodiment is manufactured by a method generally used in the art.
First, in the production of the solder powder, a known method such as a dropping method of dropping a molten solder material to obtain particles, a spraying method of centrifugal spraying, and a method of pulverizing bulk solder material can be adopted. In the dropping method or the spraying method, the dropping or spraying is preferably performed in an inert atmosphere or a solvent in order to form particles. Then, the above components can be heated and mixed to prepare a flux, and the above-mentioned solder powder is introduced into the flux, followed by stirring and mixing to produce the flux.

<Solder paste flux>
The solder paste flux of the present embodiment is used for a solder paste.
Such a flux contains rosin, a thixotropic agent, and a solvent. The flux of the present embodiment contains at least one sorbitol-based thixotropic agent selected from the group consisting of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol in an amount of from 0.2% by mass to 5.0% by mass.
The solder paste in which such a flux is used includes: As: 25 to 300 mass ppm, Pb: more than 0 mass ppm to 5100 mass ppm, and Sb: more than 0 mass ppm to 3000 mass ppm, and Bi: more than 0 mass ppm to 10,000 mass ppm. At least one of the following, and the remainder has an alloy composition composed of Sn, and contains a solder powder containing a solder alloy satisfying the following formulas (1) and (2).
275 ≦ 2As + Sb + Bi + Pb (1)
0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formulas (1) and (2), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition.

<Example of operation and effect of flux and solder paste of the present embodiment>
In the present embodiment, a rosin, a thixo agent, and a solvent are contained, and the thixo agent employs a flux containing a specific sorbitol-based thixo agent. And shape retention can be improved. In addition, a solder powder containing a solder alloy having an alloy composition in which specific elements (at least one of As, Pb and Sb and Bi) are used together with Sn at a specific ratio is employed. The solder paste in which the flux and the solder powder are combined hardly causes a change with time such as an increase in viscosity, has excellent wettability, and exhibits high mechanical properties. Furthermore, according to this solder paste, fluidity and shape retention can be improved.

  The joining method using the solder paste according to the present invention may be performed according to an ordinary method using, for example, a reflow method. The melting temperature of the solder alloy in the case of performing the flow soldering may be approximately 20 ° C. higher than the liquidus temperature. In the case of joining using the solder alloy in the present embodiment, it is preferable to consider the cooling rate at the time of solidification from the viewpoint of making the structure finer. For example, the solder joint is cooled at a cooling rate of 2 to 3 ° C./s or more. Other joining conditions can be appropriately adjusted according to the alloy composition of the solder alloy.

  For the solder alloy in the present embodiment, a low α-dose alloy can be manufactured by using a low α-dose material as a raw material. When such a low α-dose alloy is used for forming solder bumps around a memory, it is possible to suppress soft errors.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

First, a solder powder having the alloy composition shown in Tables 1 to 6 and having a size (particle size distribution) satisfying the symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1: 2014 (Test Examples 1 to 108; Examples 201 to 278) were produced.
However, Test Examples 1, 5 to 11, 13 to 15, 18, 19, 23 to 29, 31 to 33, 36, 37, 41 to 47, 49 to 51, 54, 55, 59 to 65, 67 to 69, The solder powders 72, 73, 77 to 83, 85 to 87, 90, 91, 95 to 101, 103 to 105, and 108 correspond to the solder powders specified in the present invention.

  20 parts by mass of hydrogenated rosin and 25 parts by mass of polymerized rosin as a rosin, 0.5 parts by mass of dibenzylidene (-D-) sorbitol as a thixotropic agent, 2.5 parts by mass of castor hydrogenated oil and ethylene bishydroxyl as other thixotropic agents A mixture prepared by mixing 2.5 parts by mass of stearic acid amide, 47.5 parts by mass of phenyl glycol as a solvent, 1 part by mass of glutaric acid as an organic acid, and 1 part by mass of 2-phenylimidazole as an amine, was mixed with a flux (Example) A flux having the composition shown in No. 1 was prepared.

  The above-described flux having the composition shown in Example 1 and the solder powder having the alloy compositions of the respective examples shown in Tables 1 to 6 were mixed to prepare a solder paste. The mass ratio of the flux to the solder powder was set to flux: solder powder = 11: 89.

  With respect to the case where the solder powder of each example was used, the change with time of the viscosity of the solder paste was measured. In addition, the liquidus temperature and the solidus temperature of the solder powder were measured. Furthermore, the wettability was evaluated using the solder paste immediately after the preparation. Details are as follows.

<Evaluation of change over time in viscosity of solder paste>
(1) Verification method The viscosity of each solder paste immediately after preparation was measured using PCU-205 manufactured by Malcom Corporation at a rotation speed of 10 rpm at 25 ° C. for 12 hours in the air.

(2) Criteria 基準: The viscosity after 12 hours is 1.2 times or less compared to the viscosity when 30 minutes have passed since the preparation of the solder paste.
×: The viscosity after 12 hours exceeds 1.2 times the viscosity when 30 minutes have passed since the preparation of the solder paste.

<Evaluation of ΔT>
(1) Verification method Regarding the solder powder before mixing with the flux, DSC measurement was performed using SII Nano Technology Co., Ltd., model number: EXSTAR DSC7020 at a sample amount of about 30 mg and a heating rate of 15 ° C./min. Then, a solidus temperature and a liquidus temperature were obtained. ΔT was determined by subtracting the solidus temperature from the obtained liquidus temperature.

(2) Criteria 〇: ΔT is 10 ° C. or less.
×: ΔT exceeds 10 ° C.

<Evaluation of wettability>
Each solder paste immediately after the preparation was printed on a Cu plate, heated from 25 ° C. to 260 ° C. in a N ₂ atmosphere at a rate of 1 ° C./s in a reflow furnace, and then cooled to room temperature. The wettability was evaluated by observing the appearance of the cooled solder bumps with an optical microscope.

〇: When no unmelted solder powder is observed.
×: When solder powder not completely melted was observed.

<Comprehensive evaluation (1)>
〇: In Tables 1 to 6, each of the changes over time, ΔT, and wettability were evaluated as 〇.
X: In Tables 1 to 6, at least one of the evaluations of the change over time, ΔT, and wettability was x.

  The evaluation results are shown in Tables 1 to 6.

  As shown in Tables 1 to 6, when the solder powders of Test Examples 1 to 108 were used, any of the alloy compositions satisfied all the requirements of the present invention, so that the effect of suppressing thickening, narrowing of ΔT, and excellent It was confirmed that the composition exhibited wettability.

  On the other hand, when the solder powders of Test Examples 201, 214, 227, 240, 253, and 266 were used, As did not contain As, and the result that the effect of suppressing thickening was not exhibited was shown.

  When the solder powders of Test Examples 202, 215, 228, 241, 254, and 267 were used, the results showed that the effect of suppressing thickening was not exhibited because the formula (1) was less than the lower limit.

  When the solder powders of Test Examples 203, 216, 229, 242, 255 and 268 were used, the result was inferior in wettability because the expression (2) exceeded the upper limit.

  When the solder powders of Test Examples 204, 205, 217, 218, 230, 231, 243, 244, 256, 257, 269, and 270 were used, the As content and the formula (2) exceeded the upper limits, and thus the wettability was increased. Inferior results were obtained.

  When the solder powders of Test Examples 206 to 208, 219 to 221, 232 to 234, 245 to 247, 258 to 260, and 271 to 273 are used, since the Sb content exceeds the upper limit, poor wettability results. Indicated.

  When the solder powders of Test Examples 209, 210, 222, 223, 235, 236, 248, 249, 261, 262, 274, and 275 were used, ΔT exceeded 10 ° C. because the Bi content exceeded the upper limit. The results are shown.

  When the solder powders of Test Examples 211, 213, 224, 226, 237, 239, 250, 252, 263, 265, 276, and 278 were used, ΔT exceeded 10 ° C. because the Pb content exceeded the upper limit. The results are shown.

  When the solder powders of Test Examples 212, 225, 238, 251, 264, and 277 were used, Bi and Pb were not contained, and the expression (2) was not satisfied. As a result, poor wettability was obtained.

Next, the thixotropic properties of the case where the solder powder having the alloy composition shown in Test Example 1 and the flux of each example shown in Tables 7 to 15 were used were evaluated.
In addition, for the case where the solder powder having the alloy composition shown in Test Example 1 and the flux of each example shown in Tables 8 to 15 were used, evaluation of the precipitation of crystals and generation of lumps in the flux and the solder paste was performed. .
Details are as follows.

<Evaluation of thixotropic property>
(1) Verification Method The evaluation of the thixotropic property was performed using a double cylindrical tube type rotational viscometer Malcom Viscometer PCU-205 (manufactured by Malcolm).
With respect to each solder paste, the viscosity was sequentially measured at 25 ° C. at the following rotation speed (rpm) and measurement time (min) using the above-mentioned double cylindrical tube type rotational viscometer.

  The rotational speed of the viscometer was changed in the order of 3 minutes at 10 rpm, 6 minutes at 3 rpm, 3 minutes at 4 rpm, 3 minutes at 5 rpm, 3 minutes at 10 rpm, 2 minutes at 20 rpm, 2 minutes at 30 rpm, and 1 minute at 10 rpm. Was.

From the viscosities at 3 rotations (3 rpm) and 30 rotations (30 rpm), the thixotropic ratio was determined based on the following equation.
Thixo ratio = Log (viscosity at 3 rotations / viscosity at 30 rotations)

  The evaluation was performed according to the following criteria.

(2) Criteria 基準: Thixo ratio is 0.40 or more ×: Thixo ratio is less than 0.40

<Precipitation of crystals and generation of lumps>
(1) Verification Method Regarding the fluxes of the respective examples shown in Tables 8 to 15 and the solder pastes using the same, evaluation of crystal precipitation and generation of lumps was performed by the following method. The evaluation was performed according to the following criteria.
Regarding the fluxes of the respective examples shown in Table 7 and the solder pastes using these, the evaluation of the precipitation of crystals and the generation of lumps was not performed.

Flux rating:
100 mL of each flux was collected, placed in a 200 mL glass beaker container, and stirred 10 times with a spoonful to prepare a sample for visual observation. The same operation was performed to prepare three samples for visual observation for each flux.
For each sample, the appearance after stirring 10 times was visually observed, and the state of precipitation of crystals and generation of lumps was evaluated.

Evaluation of solder paste:
Each solder paste was measured three times using a grind meter GS-2256M (manufactured by Taiyo Kiki Co., Ltd., measurement range: 0 to 100 μm). Then, the average of the three measurements was calculated, and the average was defined as the size (granularity) of the aggregates contained in the solder paste.

  The grindometer surface is provided with a groove whose depth increases at a constant value from 0 at one end to the maximum value at the other end, and a solder paste sample is skived from the maximum depth side with a scraper. Then, a linear mark or a granular mark is left at a depth corresponding to the size of the aggregate. The precipitation of crystals and the generation of lumps in the solder paste sample can be evaluated based on the depth of the position where the linear mark or the granular mark is formed.

(2) Criteria 基準: Crystals and lumps are not visually observed in the flux, and crystals and lumps are not visually observed in the solder paste.
〇: Crystals and lumps are not visually observed in the flux, and there are no crystals or lumps of 50 μm or more in the solder paste, but there are crystals or lumps of less than 50 μm.
×: Crystals and lumps were visually observed in any of the three flux samples, or crystals or lumps of 50 μm or more were present in the solder paste.

<Comprehensive evaluation (2)>
〇〇: In Tables 8 to 15, the evaluation of thixotropy is 〇, and the evaluation of precipitation of crystals and generation of lumps is ○.
〇: In Tables 8 to 15, the evaluation of thixotropy is 〇, and the evaluation of precipitation of crystals and generation of lumps is ○.
X: In Tables 8 to 15, the evaluation of thixotropy is at least x.

  The evaluation results are shown in Tables 7 to 15.

  The properties of the solder paste obtained by mixing the solder powder having the alloy composition shown in Test Example 1 with the flux having the composition shown in Example 1 (solder powder: flux = 89: 11 (mass ratio)) It was evaluated (see Example 1 in Table 7).

  As shown in Example 1, by including dibenzylidene sorbitol as a thixotropic agent within the range specified in the present invention, the thixotropic properties of the solder paste could be enhanced. That is, it was confirmed that such a solder paste had good fluidity and shape retention.

  Next, the solder powder having the alloy composition shown in Test Example 1 and the fluxes having the respective compositions shown in Examples 2 to 52 were mixed (solder powder: flux = 89: 11 (mass ratio)). A solder paste was prepared, and the properties of the solder paste were evaluated (see Tables 7 to 15).

  As shown in Examples 2 to 7, changing the amount of the sorbitol-based thixotropic agent, changing the type of the sorbitol-based thixotropic agent, and combining a plurality of types of sorbitol-based thixotropic agents can also enhance the thixotropic property of the solder paste. Was.

  As shown in Examples 8 to 13, changing the type of the sorbitol-based thixotropic agent, and further including changing the amount of the sorbitol-based additive, including the sorbitol-based additive, also resulted in the precipitation of crystals and lumps of flux and solder paste. Generation was suppressed, and the thixotropy of the solder paste was improved.

  As shown in Examples 14 to 17, by changing the type of the sorbitol-based thixotropic agent or the type of the sorbitol-based additive, the precipitation of crystals and the generation of lumps in the flux and the solder paste can be suppressed. The thixotropy of the paste was improved.

  As shown in Examples 18 to 25, by changing the type of the sorbitol-based thixotropic agent, changing the amount of the sorbitol-based thixotropic agent, changing the type of the sorbitol-based additive, changing the amount of the sorbitol-based additive, the flux and the The precipitation of crystals and the generation of lumps in the solder paste were suppressed, and the thixotropic properties of the solder paste were improved.

  As shown in Examples 26 to 31, flux and solder containing hexyl diglycol as a solvent, changing the type of sorbitol-based thixotropic agent, further including sorbitol-based additive, and changing the amount of sorbitol-based additive The precipitation of crystals and the generation of lumps in the paste were suppressed, and the thixotropy of the solder paste was improved.

  As shown in Examples 32 to 35, hexyl diglycol was contained as a solvent, the type of sorbitol-based thixotropic agent was changed, and the type of sorbitol-based additive was also changed. And the thixotropy of the solder paste could be improved.

  As shown in Examples 36 to 43, containing hexyl diglycol as a solvent, changing the type of sorbitol-based thixotropic agent, changing the amount of sorbitol-based thixotropic agent, changing the type of sorbitol-based additive, By changing the amount, the precipitation of crystals and the generation of lumps in the flux and the solder paste could be suppressed, and the thixotropy of the solder paste could be improved.

  As shown in Example 44, it is possible to suppress the precipitation of crystals and the generation of lumps in the flux and the solder paste by combining a plurality of types of rosins and by changing the amount of rosin, which contains a sorbitol-based additive. The thixotropy of the paste was improved.

  As shown in Example 45, even if the sorbitol-based additive was contained and the amount of rosin was reduced, the amount of thixo agent was increased to suppress the precipitation of crystals and the generation of lumps in the flux and solder paste. As a result, the thixotropy of the solder paste was improved.

  As shown in Examples 46 to 48, by changing the type of the halogen-based activator including the sorbitol-based additive, including the halogen-based activator, precipitation of crystals and generation of lumps in the flux and the solder paste are suppressed. Thus, the thixotropy of the solder paste could be improved.

  As shown in Example 49, even by combining a plurality of types of organic acids, the precipitation of crystals and the generation of lumps in the flux and the solder paste could be suppressed, and the thixotropy of the solder paste could be improved.

  As shown in Example 50, even when an antioxidant was included, precipitation of crystals and generation of lumps in the flux and the solder paste could be suppressed, and the thixotropy of the solder paste could be improved.

  As shown in Examples 51 and 52, by changing the amount of the other thixotropic agent, precipitation of crystals and generation of lumps in the flux and the solder paste could be suppressed, and the thixotropy of the solder paste could be improved. .

  On the other hand, as shown in Comparative Example 1, the thixotropy of the solder paste could not be improved without the sorbitol-based thixotropic agent.

  As shown in Comparative Example 2, the thixotropy of the solder paste could not be improved unless the sorbitol-based thixotropic agent was contained within the range specified in the present invention.

Next, in the same manner except that the solder powder having the alloy composition shown in Test Example 1 was changed to the solder powder having each alloy composition shown in Test Examples 2 to 108, a flux having the composition shown in Example 1 was used. By mixing (solder powder: flux = 89: 11 (mass ratio)), a solder paste was produced.
As a result, in the case of the solder paste obtained by combining the solder powders of Test Examples 2 to 108 and the flux of Example 1, the thixotropic properties were the same as in the case of the solder paste using the solder powder having the alloy composition shown in Test Example 1. Was improved, that is, it was confirmed that fluidity and shape retention were good. In addition, in these solder pastes, precipitation of crystals and generation of lumps in the flux and the solder paste could be suppressed.

Next, each of the solder powders having the respective alloy compositions shown in Test Examples 2 to 108 and each of the fluxes having the respective compositions shown in Examples 2 to 52 were mixed (solder powder: flux = 89: 11 (mass) Ratio)) to produce a solder paste.
As a result, in the case of the solder paste obtained by combining the solder powders of Test Examples 2 to 108 and the flux of Examples 2 to 52, the viscosity was increased as in the case of the solder paste using the flux having the composition shown in Example 1. It was confirmed that they exhibited a suppressing effect, narrowing of ΔT, and excellent wettability.
In the case of the solder paste in which the solder powders of Test Examples 2 to 108 and the fluxes of Examples 2 to 52 are combined, the thixotropy is enhanced, that is, the fluidity and the shape retention are good. Was confirmed. In addition, in these solder pastes, precipitation of crystals and generation of lumps in the flux and the solder paste could be suppressed.

  According to the present invention, it is possible to provide a solder paste which hardly undergoes a change over time such as an increase in viscosity, has excellent wettability, has high mechanical properties, and has good fluidity and shape retention. Further, according to the present invention, it is possible to provide a flux for a solder paste that can impart sufficient thixotropic properties, preferably suppresses crystal precipitation, and hardly causes lumps.

Claims (10)

Ru solder powder and fluxes Tona, a solder paste,
The solder powder contains at least one of As: 25 to 300 mass ppm, Pb: more than 0 mass ppm to 5,100 mass ppm, and Sb: more than 0 mass ppm to 3000 mass ppm, and Bi: more than 0 mass ppm to 10,000 mass ppm. , and the balance has an alloy composition consisting of Sn, made of solder alloy which satisfies the following formula (1) and (2),
The flux contains rosin, a thixotropic agent, and a solvent,
The content of the rosin is 15% by mass or more and 70% by mass or less based on the total amount of the entire flux.
The content of the thixotropic agent is 2% by mass or more and 15% by mass or less with respect to the total amount of the entire flux.
The thixo agent is a sorbitol-based thixo agent, which is at least one selected from the group consisting of dibenzylidene sorbitol and bis (4-methylbenzylidene) sorbitol , in an amount of 0.2% by mass or more based on the total amount of the flux . 0% by mass or less seen including,
The solder paste , wherein the solvent is at least one selected from the group consisting of aliphatic glycol solvents and aromatic glycol solvents .
275 ≦ 2As + Sb + Bi + Pb (1)
0.01 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2)
In the above formulas (1) and (2), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition. The solder paste according to claim 1, wherein the alloy composition satisfies the following expression (1a).
275 ≦ 2As + Sb + Bi + Pb ≦ 25200 (1a)
In the above formula (1a), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition. The solder paste according to claim 1, wherein the alloy composition satisfies the following expression (1b).
275 ≦ 2As + Sb + Bi + Pb ≦ 5300 (1b)
In the above formula (1b), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition. The solder paste according to any one of claims 1 to 3, wherein the alloy composition satisfies the following expression (2a).
0.31 ≦ (2As + Sb) / (Bi + Pb) ≦ 10.00 (2a)
In the above formula (2a), As, Sb, Bi and Pb each represent the content (mass ppm) in the alloy composition.   5. The method according to claim 1, wherein the alloy composition contains at least one selected from the group consisting of Ag: 0 to 4% by mass and Cu: 0 to 0.9% by mass. 6. Solder paste.   The thixotropic agent is at least one sorbitol-based additive selected from the group consisting of (D-) sorbitol, monobenzylidene (-D-) sorbitol, and mono (4-methylbenzylidene)-(D-) sorbitol. The solder paste according to any one of claims 1 to 5, comprising: The solder paste according to claim 6, wherein a ratio (mass ratio) of the sorbitol-based additive to the sorbitol-based thixotropic agent is 0.03 % or more and 1.50 % or less . 8. The solder paste according to claim 1, further comprising 0.5 to 10 % by mass of at least one selected from the group consisting of an ester compound and an amide compound , based on the total amount of the entire flux . 9. The solder paste according to any one of claims 1 to 8 , further comprising an organic acid in an amount of 0 mass% to 10 mass% based on the total amount of the entire flux . Furthermore, the total amount of the entire flux amine than 5 mass% or more 0 wt%, the organic halogen compound or less 8.0 wt% or more 0 wt%, the amine hydrohalides or 0 wt% 5.0 The solder paste according to any one of claims 1 to 9 , wherein the solder paste contains 0% by mass or less and 8% by mass or less of an antioxidant.