JP2012006054A - Solder alloy, and solder joined body using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new solder alloy capable of suppressing over a long period of time, the change over time such as the material oxidation of the solder alloy or the blackening of the surface of a solder-joined part while maintaining the characteristics of a lead-free solder alloy capable of soldering an oxide material such as glass and ceramics, and also to provide a solder-joined body using the alloy.SOLUTION: The new solder alloy comprises, by mass, 0.5-9.0% Zn, 0.1-4.0% Sb, 0.005-0.500% Cr and the balance Sn with inevitable impurities, and may contain ≤0.2% Al.

Description

  The present invention relates to a solder alloy capable of suppressing blackening of the solder surface of a solder joint due to change over time while maintaining excellent joint strength to an oxide material such as glass or ceramic, and a solder joint body using the same. Is.

As a lead-free solder alloy that can be bonded to an oxide material such as glass, a Sn—Zn—Sb—Al solder alloy is proposed in Patent Document 1. The solder alloy disclosed in Patent Document 1 is added with a predetermined amount of Zn in order to ensure the bonding ability with the oxide material, and in order to suppress white turbidity at the bonding interface between the solder alloy and the glass. By adding Sb and Al, excellent characteristics thereof are obtained.
The solder alloy of Patent Document 1 can be bonded at a temperature lower than that of a general glass frit, and is a solder alloy in consideration of the recent environmental problems. Moreover, since the solder alloy of patent document 1 can be joined directly with an oxide material, it does not require pre-processing to oxide materials, such as glass, and has the possibility of simplifying the conventional construction method.

Japanese Patent Laid-Open No. 2004-082199

  According to the study by the present inventors, when the joined body joined to the oxide material such as glass using the solder alloy of Patent Document 1 described above is held for a long time in the atmosphere containing moisture, the metal on the solder surface A new problem has been confirmed, which is the loss of luster and blackening, and the aging of the solder.

  Such changes in the solder alloy over time cause deterioration in bonding strength and airtightness in applications where the solder alloy is directly exposed to the outside air, such as a pair of glasses, making it difficult to obtain sufficient long-term reliability. Further, in applications that require design properties such as furniture, there is a big problem such as lowering the product value.

  In view of the above problems, the object of the present invention is to maintain the characteristics of a lead-free solder alloy that can be joined to an oxide material such as glass or ceramic, and to oxidize the solder alloy and to blacken the solder surface of the solder joint. It is an object of the present invention to provide a new solder alloy and a solder joined body using the same, which can suppress a change with time over a long period of time.

  As a solder alloy used for joining with an oxide material such as glass, the present inventors can add a specific amount of Sb and Cr to a main component of Sn and Zn, thereby changing the solder alloy over time. The inventors have found that a new effect of being able to be suppressed is obtained, and have reached the present invention.

That is, solder containing Zn: 0.5 to 9.0%, Sb: 0.1 to 4.0% and Cr: 0.005 to 0.500%, and remaining Sn and inevitable impurities in mass% It is an alloy.
Moreover, it is preferable that the solder alloy of this invention is the mass% and is Zn: 1.5-6.5%.
Moreover, it is preferable that the solder alloy of this invention is mass% and is Sb: 1.0-3.5%.
Moreover, it is preferable that the solder alloy of this invention is the mass% and is Cr: 0.010-0.400%.
Moreover, the solder alloy of this invention can contain Al: 0.2% or less by the mass%.
Moreover, the solder alloy of the present invention is suitable for joining members having oxide or oxidized surfaces.
Moreover, the member which has an oxide or an oxidation surface can be joined by the solder alloy of this invention, and an inexpensive solder joined body can be provided.

  The solder alloy of the present invention is suitable for wiring bonding with a transparent conductive film formed on a glass substrate such as a sealing or solar cell such as a pair glass or a glass container. The industrial value is extremely large because it is possible to suppress the time-dependent change of the solder and improve the design reliability due to the joining reliability and blackening.

As described above, an important feature of the present invention is that an alloy obtained by adding a specific amount of Sb and Cr to a Sn—Zn solder alloy is employed.
Hereinafter, the reason for limiting the component composition (mass%) of the solder alloy of the present invention will be described.

Zn: 0.5-9.0%
Zn is a basic element for bonding with an oxide material such as glass or ceramic. The joining mechanism of the solder alloy of the present invention is such that Zn having a higher oxygen affinity than Sn is contained in the solder alloy so that the Zn-based oxide film formed on the surface of the molten solder is on the surface of an oxide material such as glass. It is thought that it joins by forming an oxide layer.
The Zn content needs to be 0.5% or more in order to obtain sufficient bonding strength with an oxide material such as glass. In order to obtain higher bonding strength, 1.5% or more is preferable. Moreover, it is more preferable to contain 2.0% or more.
On the other hand, when Zn is excessively added to the solder alloy, a large amount of dross is generated during soldering, which becomes a factor that impedes wettability with an oxide material such as glass. In addition, when a solder alloy containing Zn is held for a long time in an atmosphere containing moisture, blackening of the solder surface is promoted. Therefore, in the present invention, the Zn content is 9.0% or less. Preferably, it is 6.5% or less, more preferably 4.5% or less.

Sb: 0.1-4.0%
Sb is an essential element for suppressing oxidation of the solder alloy material. Although detailed verification has not been made, it is considered that Sb is dissolved in Sn so that excessive oxidation of Zn in the solder alloy is suppressed and a change with time of the solder alloy is suppressed.
The content of Sb is required to be 0.1% or more in order to prevent excessive oxidation of Zn and to obtain a sufficient effect of suppressing change with time of the solder alloy. Furthermore, 1.0% or more is preferable in order to obtain a long-term change suppressing effect. Moreover, it is more preferable to contain 1.5% or more.
On the other hand, when the content of Sb in the solder alloy is too large, there is a concern that the bonding strength with an oxide material such as glass is lowered. Therefore, in the present invention, the Sb content is 4.0% or less. Preferably, it is 3.5% or less, More preferably, it is 2.5% or less.

Cr: 0.005 to 0.500%
Cr is the most important element for suppressing blackening of the solder surface of the joined body to which the solder alloy of the present invention is soldered. Cr added to the Sn—Zn—Sb solder alloy forms a Cr oxide film on the surface of the molten solder when soldering with an oxide material such as glass. In the solder alloy of the present invention, this Cr-based oxide film is considered to suppress the blackening of the solder surface. Moreover, Cr suppresses generation | occurrence | production of the dross during soldering and contributes also to joining with oxide materials, such as glass.
The Cr content needs to be 0.005% or more in order to obtain an effect of suppressing blackening of the solder surface. Furthermore, in order to obtain a long-term blackening suppressing effect, 0.010% or more is preferable. Moreover, it is preferable to contain 0.050% or more.
On the other hand, when Cr is excessively added to the solder alloy, the melting temperature of the solder rises, thereby raising the soldering temperature to the oxide material or the like and lowering the working efficiency. Therefore, in the present invention, the Cr content is 0.500% or less. Preferably, it is 0.400% or less, More preferably, it is 0.200% or less.

Al: 0.2% or less Al can also be contained in the solder alloy of the present invention. Al is an element that contributes to suppression of solder dross generation during soldering or melting, and bonding to an oxide material such as glass.
However, when a large amount of Al is contained, the Al-based intermetallic compound formed in the solder alloy causes component segregation, resulting in a manufacturing problem that the above characteristics cannot be obtained stably. Therefore, it is preferable to add 0.2% or less of Al to the solder alloy of the present invention. More preferably, it is 0.1% or less.
Further, in order to clearly obtain the effect of Al, 0.005% or more is preferable, and more preferably 0.01% or more.

The remaining Sn and unavoidable impurities Sn are basic elements constituting the solder alloy of the present invention that act to lower the melting temperature. In particular, in order to set the melting temperature of the solder to 230 ° C. or lower, it is desirable to mix Sn by 88% or more. More preferably, it is 90% or more.

  Inevitable impurities include P, Si, Bi, and Ga. P and Si inhibit the wettability of the solder. Bi and Ga become factors that lower the corrosion resistance of the solder alloy when held for a long time in an atmosphere containing moisture. Ga also causes voids. Therefore, the total of these elements is preferably regulated to 50 ppm or less. More preferably, it is 10 ppm or less in total.

The solder alloy of the present invention exhibits excellent bonding ability not only to ceramics such as alumina and soda lime glass but also to members having any oxide and oxidized surface.
In addition, the solder alloy of the present invention can exhibit excellent bonding ability even if it is a difficult-to-bond material such as Al, Si, or Ti that has been difficult to solder due to the influence of the oxidized surface.
In addition, the solder alloy of the present invention is not only a member having the above oxide and oxide surfaces, nitrides and difficult-to-join materials, but also to an ITO, Mo, Al, Cr film, etc. formed on a glass substrate. Suitable.
In addition, the solder alloy of the present invention is not only used for joining the above-mentioned oxide and oxide surface / nitride or between each other, but a member having an oxide and an oxide surface that can ensure the joining ability. A material other than nitride may be used. For example, the solder alloy of the present invention has bonding ability to metals such as Al-based alloys, various stainless steels, copper and Fe-Ni-based alloys. If the surface treatment for giving is given, use will not be restricted.
Moreover, the solder alloy of this invention can also be used as a substitute of the soldering | grounding process by apply | coating to the member and nitride surface which have an oxide and an oxidation surface.

  The solder alloy of the present invention has excellent bonding strength and airtightness with respect to a bonding member using an oxide material, and is suitable for, for example, a pair glass, a display, a vacuum container, or a gas sealed container.

For joining with difficult-to-join materials such as oxides and nitrides using the solder alloy of the present invention, for example, for fixing metal wiring on a glass substrate, a molten solder is applied on a glass substrate at room temperature. It becomes possible. Also, for sealing hermetic containers such as paired glass and displays, the soldering iron must be heated sufficiently in consideration of the heat capacity of the material to be joined, or by heating the member to be joined above the liquidus line of the solder alloy. This is possible by preheating the material to be joined below the liquidus of the solder alloy.
In joining to the material to be joined, it is effective to apply ultrasonic vibration to the solder alloy in order to take in oxygen into the molten solder and promote wetting to the material to be joined.

After weighing Sn, Zn, Sb, Cr and Al so as to have the composition shown in Table 1, high-frequency melting was performed in an Ar atmosphere, and the obtained molten alloy was poured into a mold to prepare a solder alloy. Moreover, No. which added Sn, Zn, and Sb which are comparative examples. 6 was dissolved in the atmosphere and poured into a mold to prepare a solder alloy. In addition, P, Si, Bi, and Ga, which are impurity elements not described in Table 1, were 50 mass ppm or less in total.
The obtained solder alloy was evaluated by the following test method in order to confirm the effect of suppressing the temporal change of the solder alloy. In this evaluation, the solder alloy was used after being processed into a wire rod having a diameter of 1 mm and a small piece having a 3 mm square and a length of 15 mm for easy soldering.

(Evaluation Test 1)
A borosilicate glass (product name TEMPAX) cut into a 30 mm square and a thickness of 3 mm was used as a material to be joined, and a glass plate was placed on a hot plate, and then the glass plate was heated to about 260 ° C. Thereafter, the solder alloy prepared above was placed on a heated glass plate, and ultrasonic vibration was applied to a soldering iron heated to about 370 ° C. (ultrasonic soldering device SUNBUNDER USM-III manufactured by Kuroda Techno Co., Ltd.) A test piece was prepared by coating the entire surface of the glass plate so that the thickness of the solder alloy was about 120 μm and gradually cooling in the air.

Next, the test piece prepared above was left as an accelerated environmental test in a high-temperature and high-humidity tester (HIFLEX FH06C manufactured by Enomoto Kasei Co., Ltd.) at 85 ° C. and 85 RH% for 1168 hours. At this time, in any of the test pieces using the solder alloy of the present invention, no white turbidity was observed in the solder joint portion, which appears to be caused by oxidation or the like from the joint interface between the solder and the glass plate.
In order to confirm the effect of suppressing the time-dependent change of the solder surface applied to one surface of the glass plate, the reflectance (Y) defined by the CIE 1931 Yxy color system is measured, and the change in the metallic luster due to the blackening of the solder surface Evaluated. The reflectance was measured by using a spectrocolorimeter (MINOLTA CM-2600d manufactured by Konica Minolta Sensing Co., Ltd.) before (Y _B ) and after (Y _A ) the solder surface before the acceleration environment test. The effect of suppressing the blackening of the solder surface was evaluated rate of change (%) in _{((Y B -Y A) /} Y B) × 100 (%). In addition, the light-receiving range at this time was 8 mm in diameter, and the reflectance was an average value of the values obtained by measuring four different locations on the solder surface.

  As shown in Table 1, the rate of change of each of the inventive examples is 36.0% or less, and the decrease in reflectance is suppressed and the solder surface is glossy, whereas the rate of change of the comparative example is , Both exceeded 40.0%, the drop in reflectance was large, and the gloss of the solder surface was lost. From this, it was confirmed that the solder alloy of the present invention can suppress blackening of the solder surface even in an accelerated environment test by adding a specific amount of Cr. Moreover, it has also confirmed that the solder alloy of this invention acquired the effect of the more excellent blackening suppression by adding Al further.

Next, the brightness defined by the CIE 1976 L ^* a ^* b ^* color system was measured, and the change in metallic luster due to blackening of the solder alloy surface was evaluated. The brightness was measured using a spectrocolorimeter (MINOLTA CM-2600d manufactured by Konica Minolta Sensing Co., Ltd.) before and after the accelerated environmental test (L ^* _B ) and after (L ^* _A ). The effect of suppressing the blackening of the solder surface was evaluated by a brightness difference obtained by subtracting the L ^* _B value before the test from the L ^* _A value after the test. In addition, the light-receiving range at this time was 8 mm in diameter, and the brightness was an average of the values obtained by measuring four locations on the solder surface.

  As shown in Table 1, the brightness differences of the inventive examples were all smaller than -15.0% and bright, whereas the brightness differences of the comparative examples were both larger than -17.0% and dark. . From this, it was confirmed that the solder alloy of the present invention can suppress blackening of the solder surface even in an accelerated environment test by adding a specific amount of Cr. It has also been confirmed that the solder alloy of the present invention can obtain a better blackening suppression effect by further adding Al.

After weighing Sn, Zn, Sb, Cr and Al so as to have the composition shown in Table 2, high-frequency melting was performed in an Ar atmosphere, and the obtained molten alloy was poured into a mold to prepare a solder alloy.
The obtained solder alloy was evaluated by the following test method in order to more quantitatively evaluate the bonding strength and material oxidation. In addition, P, Si, Bi, and Ga, which are impurity elements not described in Table 2, were 50 ppm by mass or less in total. In this evaluation, the solder alloy was used after being processed into a wire having a diameter of 1 mm so that the soldering can be easily performed.

(Evaluation Test 1)
A borosilicate glass (product name TEMPAX) cut into a 30 mm square and a thickness of 3 mm was used as a material to be joined, and a glass plate was placed on a hot plate, and then the glass plate was heated to about 260 ° C. Thereafter, the solder wire prepared above is placed on a heated glass plate, and ultrasonic vibration is applied to a soldering iron heated to about 370 ° C. (ultrasonic soldering device SUNBUNDER USM-III manufactured by Kuroda Techno Co., Ltd.) A test piece was prepared by coating the entire surface of the glass plate so that the thickness of the solder alloy was about 110 μm and gradually cooling in the air.

In order to confirm the effect of suppressing the white turbidity of the solder joints, which are thought to be caused by oxidation, etc. from the joint interface between the solder and the glass plate, the test piece prepared above was used as an accelerated environment test at 85 ° C. and 85 RH%. The test piece was left for 1000 hours in a humidity tester (HIFLEX FH06C manufactured by Enomoto Kasei Co., Ltd.).
The cloudiness region of the solder joint portion of the test piece after the accelerated environment test was evaluated by observing the joint portion between the solder and the glass plate from the glass side, measuring the cloudy area with respect to the entire surface of the 30 mm square glass plate, and evaluating the area ratio.

  As shown in Table 2, the cloudiness area ratio of the joint between the solder and the glass plate was 0% in both the inventive examples and the comparative examples. From this, the solder alloy of this invention has confirmed that the cloudiness of the junction part of the solder equivalent to a comparative example and a glass plate can be suppressed by adding a specific amount of Sb even after an accelerated environment test.

(Evaluation test 2)
As a material to be joined, a peel test piece was produced by cutting the solder surface of the sample piece produced in the same manner as the above-described production method with a cutter knife so as to form a 5 × 5 grid of 5 mm square grids. .
Then, the peel specimen was used as an accelerated environment test, and the specimen was left for 1000 hours in a high-temperature and high-humidity tester (HIFLEX FH06C manufactured by Enomoto Kasei Co., Ltd.) at 85 ° C. and 85 RH%.

  In order to confirm the change in the bonding strength of the solder due to the change over time, a peel test was performed on the peel test pieces before and after the accelerated environment test. In the peel test, an adhesive tape (CT-405AP-24 manufactured by Nichiban Co., Ltd.) was attached to one surface of the test piece, a three-time peeling test was performed, and the areas where the solder was peeled were counted. In the peel test, in order to ignore the influence of the edge portion among the 5 × 5 cells, the evaluation was performed with a total of 9 cells of the 3 × 3 cells in the center.

  As shown in Table 2, before the accelerated environment test, it was confirmed that both the solder alloys of the present invention example and the comparative example had sufficient strength without peeling. Similarly, after the accelerated environment test, no peeling occurred in the solder alloys of the present invention example and the comparative example. From this, it has confirmed that the solder alloy of the example of the present invention has a bonding strength equivalent to that of the comparative example by adding a specific amount of Zn even after the accelerated environmental test.

(Evaluation Test 3)
In order to evaluate the material oxidation of the solder alloy, the solder alloy produced as described above was allowed to stand for 1000 hours in a high-temperature and high-humidity tester (HIFLEX FH06C manufactured by Enomoto Kasei Co., Ltd.) at 85 ° C. and 85 RH% as an accelerated environment test. .
The oxygen value of the solder alloy was measured with EMGA-620W manufactured by Horiba.

As shown in Table 2, it was 30 mass ppm or less before the accelerated environmental test in both the inventive example and the comparative example.
After the accelerated environment test, the oxygen value of the solder alloy was 100 mass ppm or less in both the inventive example and the comparative example. From this, it was confirmed that the solder alloy of the present invention example can suppress material oxidation as well as the comparative example by adding a specific amount of Sb even after the accelerated environment test.

Claims (7)

  It is characterized by comprising Zn: 0.5 to 9.0%, Sb: 0.1 to 4.0% and Cr: 0.005 to 0.500%, and remaining Sn and inevitable impurities. Solder alloy.   2. The solder alloy according to claim 1, wherein the content of Zn is 1.5 to 6.5% by mass.   The solder alloy according to claim 1, wherein Sb is 1.0 to 3.5% by mass.   The solder alloy according to any one of claims 1 to 3, wherein Cr: 0.010 to 0.400% in mass%.   The solder alloy according to any one of claims 1 to 4, characterized by containing, by mass%, Al: 0.2% or less.   The solder alloy according to any one of claims 1 to 5, wherein a member having an oxide or an oxidized surface is joined.   6. A solder joint comprising a member having an oxide or an oxidized surface joined with the solder alloy according to claim 1.