Patent Description:
As a conventional solder alloy and a bonded structure using the same, for example, a brazing filler metal containing Sb in a range of <NUM> mass% to <NUM> mass%, Te in a range of <NUM> mass% to <NUM> mass%, and the balance of Sn, optional additives, and inevitable impurities, and a semiconductor apparatus which is assembled by the brazing filler metal is disclosed in <CIT>. <CIT> relates to a lead-free solder alloy suitable for bonding inside electronic components.

In the solder alloy disclosed in <CIT>, although Te, Ag, Cu, Fe, and Ni are added to Sn so as to improve the bonding reliability, the temperature cycle test is performed only for <NUM> cycles. Therefore, there was a concern in that the bonding reliability was insufficient for the purpose such as on-board which requires reliability enough to withstand the temperature cycle test of <NUM> cycles or more. The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a solder alloy that enhances crack resistance of a solder bonded portion and realizes high reliability.

A solder alloy of the invention is provided according to claims.

According to the invention there is provided a solder alloy for enhancing the crack resistance of a solder bonded portion and realizes high reliability, and a bonded structure using the same.

Prior to detailed description, problems in the related art will be briefly described.

In the solder alloy of the invention the content of Sb is in a range of <NUM> wt% to <NUM> wt%, the content of Te is in a range of <NUM> wt% to <NUM> wt%, the content of Au is in a range of <NUM> wt% to <NUM> wt%, comprises at least one of Ag and Cu, wherein the content of Ag in the solder alloy is in a range of <NUM> wt% to <NUM> wt%, the content Cu is equal to or greater than <NUM> wt% and less than <NUM> wt%, the total content of Ag and Cu is in a range of <NUM> wt% to <NUM> wt%, and the balance is Sn.

In the specification, "content" is the ratio of the weight of each element to the total weight of the solder alloy and is expressed in unit of wt% (weight percent).

In the specification, "solder alloy" may include trace metals (for example, less than <NUM> wt%) that inevitably contaminate as long as its metal composition is substantially composed of the listed metals. The solder alloy may have any form and may be used for soldering alone, for example, or in combination with other materials (for example, flux) other than metal.

In the solder alloy of the disclosure, Te is added so as to have a predetermined content, and thus elongation due to solid solution of Te in Sn has been improved. Further, since the solder alloy of the disclosure is added so that both Te and Au have a predetermined content, Au having different ionic radius at high temperature is complicatedly substituted with Te which is solidly dissolved in Sn so as to cause dislocation, and thereby the elongation at high temperature has been improved. Therefore, the solder alloy of the disclosure has more excellent elongation at high temperature as compared with the SnSb-based solder to which Te is added alone. As a result, it is possible to absorb the repetitive stress generated during the heat cycle, and thereby the high reliability of the bonded structure can be realized. Since at least one of Ag and Cu is contained in the solder alloy of the disclosure, an intermetallic compound of Ag and Sn, or Cu and Sn is precipitated. When the intermetallic compound is precipitated, the bonding strength is improved, and thereby the high reliability of the bonded structure can be realized.

In the bonded structure of one embodiment, a semiconductor device and a circuit board are bonded to each other via a solder bonded layer containing Sb, Te, Au, and at least one of Ag and Cu, and a SnNi alloy and a SnCu alloy are formed on an interface between a metallized layer of the semiconductor device, a plated layer of the circuit board, and the solder bonded layer.

The solder bonded layer of the bonded structure of the embodiment contains Te and Au, and thus elongation at high temperature and room temperature is improved, and the crack resistance is excellent in the heat cycle. Therefore, the high reliability in the bonded structure of the disclosure can be realized.

Hereinafter, the exemplary embodiment of the solder alloy of the disclosure will be described with reference to the drawings.

Solder alloy <NUM> is an alloy which contains Sb (antimony), Te (tellurium), Au (gold), and at least one of Ag (silver), and Cu (copper), and the balance of Sn (tin).

The content of Sb in solder alloy <NUM> is in a range of <NUM> wt% to <NUM> wt%. The content of Sb in the solder alloy is in such a range, the thermal fatigue characteristic of the solder bonded portion can be improved. When the content of Sb in solder alloy <NUM> is in a range of <NUM> wt% to <NUM> wt%, it is possible to effectively cause the solid solution of Sn in Sb, and thereby the strength and the elongation of solder alloy <NUM> can be effectively improved.

In solder alloy <NUM>, the content of Te is in a range of <NUM> wt% to <NUM> wt%, the content of Au is in a range of <NUM> wt% to <NUM> wt%, and the balance is Sn. Here, in solder alloy <NUM>, Au may be provided to perform plating on the surface of solder alloy <NUM> containing Sb, Te, and at least one of Ag and Cu, and the balance of Sn. In this case, Au is melted into solder alloy <NUM> at the time of melting solder alloy <NUM>. Since the solder alloy of the disclosure is added so that both Te and Au have a predetermined content, Au having different ionic radius at high temperature is complicatedly substituted with Te which is solidly dissolved in Sn so as to cause dislocation, and thereby the elongation at high temperature has been improved. Therefore, the solder alloy of the disclosure has more excellent elongation at high temperature as compared with the SnSb-based solder to which Te is added alone. Therefore, it is possible to absorb the repetitive stress generated during the heat cycle, and to enhance the crack resistance, and thereby the high reliability of the bonded structure can be realized.

In solder alloy <NUM>, the content of Ag is in a range of <NUM> wt% to <NUM> wt%, is further preferably in a range of <NUM> wt% to <NUM> wt%, the content Cu is equal to or greater than <NUM> wt% and less than <NUM> wt%, and the total content of Ag and Cu is in a range of <NUM> wt% to <NUM> wt%. When the content of at least one of Ag and Cu is in said ranges, it is possible to effectively precipitate the intermetallic compound of Ag and Sn, or Cu and Sn. As a result, it is possible to improve the bonding strength of the solder alloy, and thereby the high reliability of the bonded structure can be realized. When at least one of Ag and Cu is within said ranges, the intermetallic compound of Ag and Sn, or Cu and Sn accelerates transfer of Te, Sb and Au, or the like which is solidly dissolved in Sn, and thereby it is possible to improve the elongation at high temperature of the solder alloy as compared with a case where only Te is added. When at least one of Ag and Cu is within said ranges, intermetallic compound AgsSn of Ag and Sn, or intermetallic compound Cu<NUM>Sn<NUM> of Cu and Sn are precipitated, the strength is improved at high temperature and the crack resistance can be enhanced.

Solder alloy <NUM> can be obtained in various sizes depending on the bonded structure to be manufactured, and for example, solder alloy <NUM> having <NUM><NUM> in size and the thickness in a range of <NUM> to <NUM>. When the thickness of solder alloy <NUM> is equal to or smaller than <NUM>, the thermal resistance of the solder bonded portion to be formed is not increased and the heat of semiconductor device <NUM> can be efficiently released. When the thickness of solder alloy <NUM> is equal to or larger than <NUM>, it is possible to suppress the occurrence of voids at the time of solder bonding, and thereby the thermal resistance of the solder bonded portion can be reduced.

Next, the bonded structure of the exemplary embodiment of the disclosure will be described with reference to the drawings.

In <FIG>, semiconductor device <NUM> includes silicon chip <NUM>, ohmic layer <NUM> formed on the lower surface of silicon chip <NUM>, and formed metallized layer <NUM> on the lower surface of ohmic layer <NUM>. In terms of ease of manufacture, silicon chip <NUM> preferably has a vertical length of <NUM>, a horizontal length of <NUM>, and a thickness of <NUM>; however, the size is not limited thereto, and the various sizes can be used.

Ohmic layer <NUM> of semiconductor device <NUM> is a layer formed of an optional pure metal or an alloy, and the material thereof is not limited; for example, Ti, Al, Cr, Ni, or an alloy containing all of them can be used. When the above metal is used in the ohmic layer, an appropriate ohmic bonding can be obtained. The thickness of ohmic layer <NUM> is not particularly limited, and for example, it may be in a range of <NUM> to <NUM>, or may be <NUM>. When ohmic layer <NUM> has such a thickness, it is likely to secure low resistance value and the bonding reliability.

Metallized layer <NUM> of semiconductor device <NUM> is a layer formed of an optional pure metal or an alloy, and the material thereof is not limited; for example, Ni, Cu, or an alloy containing all of them can be used. The thickness of metallized layer <NUM> is not particularly limited, and for example, it may be in a range of <NUM> to <NUM>, or may be <NUM>. When metallized layer <NUM> has such a thickness, it is possible to firmly bond with solder alloy.

Circuit board <NUM> includes lead frame <NUM> and plated layer <NUM> formed on the surface of lead frame <NUM>.

For the material of lead frame <NUM> of circuit board <NUM>, a material having good thermal conductivity such as metal or ceramics can be used. The material of lead frame <NUM> is not limited to the above materials, and for example, it is possible to use copper, aluminum, alumina, aluminum nitride, silicon nitride, and the like. In terms of ease of manufacture, lead frame <NUM> preferably has a vertical length of <NUM>, a horizontal length of <NUM>, and a thickness of <NUM>; however, the size is not limited thereto, and the various sizes can be used.

Plated layer <NUM> of circuit board <NUM> is a layer formed of an optional pure metal or an alloy, and the material thereof is not limited; for example, Ni, Cu, or an alloy containing all of them can be used. The thickness of the plated layer is not particularly limited, and for example, it may be in a range of <NUM> to <NUM>, or may be <NUM>. When the plated layer has such a thickness, it is possible to firmly bond with solder alloy.

Bonded structure <NUM> manufactured by using the solder alloy of the disclosure is schematically illustrated in <FIG>. Bonded structure <NUM> is configured in which semiconductor device <NUM> and circuit board <NUM> are bonded to each other via alloy layer <NUM> and solder bonded layer <NUM>.

In order to manufacture the bonded structure <NUM>, as illustrated in <FIG>, solder alloy <NUM> is placed on plated layer <NUM> of circuit board <NUM>, and semiconductor element <NUM> is placed on solder alloy <NUM> such that solder alloy <NUM> and metallized layer <NUM> of semiconductor device <NUM> are in contact with each other. Subsequently, when heating is performed from room temperature to <NUM> while increasing the temperature by <NUM> per minute, after holding at <NUM> for one minute, and cooling is performed from <NUM> to room temperature while decreasing the temperature by <NUM> per minute, alloy layer <NUM> is formed between solder alloy <NUM>, metallized layer <NUM>, and plated layer <NUM>, and thereby it is possible to manufacture bonded structure <NUM> as illustrated in <FIG>.

In such a manufacturing process of the bonded structure, alloy layer <NUM> of bonded structure <NUM> is an intermetallic compound formed on an interface between metallized layer <NUM> of the semiconductor device, the plated layer of circuit board108, and solder bonded layer <NUM>. In a case where Ni or Cu is contained in metallized layer <NUM> and plated layer <NUM>, a SnNi (tin-nickel) alloy is contained in alloy layer <NUM>. When the SnNi alloy or the SnCu alloy is formed on alloy layer <NUM> between metallized layer <NUM>, plated layer <NUM> of the circuit board, and solder bonded layer <NUM>, metallized layer <NUM>, plated layer <NUM> of the circuit board, and solder bonded layer <NUM> are bonded by metal, and thereby it is possible to excellent bonding strength. At least one of Te and Au may be contained in the SnNi alloy and the SnCu alloy which can be contained in alloy layer <NUM>, and when at least one of Te and Au is contained in the SnNi alloy and the SnCu alloy, alloy layer <NUM> becomes a multinary alloy, the strength of the alloy is improved, and occurrence of cracks in alloy layer <NUM> can be suppressed even when stress is applied due to a heat cycle or the like. Solder bonded layer <NUM> of bonded structure <NUM> contains metal elements such as Sb, Te, Au, Ag, and Cu contained in solder alloy <NUM>, and has substantially the same composition as that of solder alloy <NUM> before bonding; however, in solder bonded layer <NUM>, the content of Sn is decreased by the rate at which Sn reacts at the time of forming alloy layer <NUM>.

As indicated in Table <NUM>, a plurality solder alloys <NUM> containing different contents of Sb, Te, Au, Ag, and Cu, and the balance of Sn are prepared so as to conduct a tensile test at an ambient temperature of <NUM>. For the tensile test, an evaluation sample in which the solder alloy was cast in a dumbbell shape was prepared. Regarding the shape of the evaluation sample, a portion fixed in a testing machine is set to have <NUM> in diameter, and <NUM> in the length, and a dumbbell narrow portion has <NUM> in diameter and <NUM> in the length. The tensile test of the evaluation sample was conducted by setting an interval between upper and lower sample fixing jigs of the tensile testing machine to be <NUM>, fixing the evaluation sample, setting the ambient temperature to be <NUM>, and then pulling the evaluation sample with the tensile testing machine so that only the axial force of the evaluation sample is applied.

The tensile strength (MPa) of the evaluation sample is a stress corresponding to the maximum force applied during the test when the tensile test is conducted at a strain rate of <NUM> × <NUM>-<NUM>/s with respect to <NUM> of interval of the fixed jig before the test.

The elongation (%) of the evaluation sample is the ratio of increment of the fixing jig interval when the evaluation sample was broken in the tensile test with respect to <NUM> of interval of the fixing jig before the test. For example, in a case where the interval of the fixing jig is <NUM> when the evaluation sample is broken, the elongation is (<NUM> - <NUM>)/<NUM> × <NUM> = <NUM> (%).

The measurement results of the tensile strength (MPa) and the elongation (%) in the tensile test are also indicated in Table <NUM>.

Example <NUM>-<NUM> and Example <NUM>-<NUM> are solder alloys of the disclosure which do not contain Cu but contain Ag. In Example <NUM>-<NUM>, the content of Sb was <NUM> wt%, the content of Te was <NUM> wt%, the content of Au was <NUM> wt%, and the content of Ag was <NUM> wt%. In Example <NUM>-<NUM>, the content of Sb was <NUM> wt%, the content of Te was <NUM> wt%, the content of Au was <NUM> wt%, and the content of Ag was <NUM> wt%. In Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%. In Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%. In any of Example <NUM>-<NUM> and Example <NUM>-<NUM>, it is possible to obtain excellent effects.

Example <NUM>-<NUM> and Comparative Example <NUM>-<NUM> are solder alloys which do not contain Ag but contain Cu. In Example <NUM>-<NUM>, the content of Sb was <NUM> wt%, the content of Te was <NUM> wt%, the content of Au was <NUM> wt%, and the content of Cu was <NUM> wt%. In Comparative Example <NUM>-<NUM>, the content of Sb was <NUM> wt%, the content of Te was <NUM> wt%, the content of Au was <NUM> wt%, and the content of Cu was <NUM> wt%. In Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%. In Comparative Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%. In any of Example <NUM>-<NUM> and Comparative Example <NUM>-<NUM>, it is possible to obtain excellent effects, but Comparative Example <NUM>-<NUM> is not included in the present invention.

In Comparative Example <NUM>-<NUM> and Comparative Example <NUM>-<NUM>, neither Ag nor Cu was used. In Comparative Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%. In Comparative Example <NUM>-<NUM>, the strength was <NUM> MPa and the elongation was <NUM>%.

From the above results, it has been made clear that the elongation and tensile strength of solder alloy <NUM> can be improved by containing Ag or Cu. The reason for this is due to the effect of solid solution of Te and Au in a Sn parent phase, and precipitation of intermetallic compounds of Ag and Sn, or Cu and Sn by containing Ag or Cu. As a result, it is possible to absorb the repetitive stress generated during the heat cycle, and thereby the high reliability of the bonded structure can be realized.

As indicated in Tables <NUM> to <NUM>, solder alloys <NUM> in Examples and Comparative Examples <NUM>-<NUM> to <NUM> - <NUM>, which contain different contents of Sb, Te, Au, Ag, and Cu, and the balance of Sn, were prepared, and bonded structure <NUM> was manufactured by using each of prepared solder alloys <NUM>.

Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> in table <NUM> are Reference Examples. Any of bonded structures <NUM> having solder alloys <NUM> of Examples and Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> was manufactured by the following method using the following members.

Semiconductor device <NUM> having a configuration in which ohmic layer <NUM> formed of Ti is provided on the lower surface of silicon chip <NUM> which has a vertical length of <NUM>, a horizontal length of <NUM>, and a thickness of <NUM>, and metallized layer <NUM> formed on Ni is provided on the lower surface of ohmic layer <NUM> was prepared. Circuit board <NUM> having a configuration in which a lead frame formed of copper which has a vertical length of <NUM>, a horizontal length of <NUM>, and a thickness of <NUM> is provided, and plated layer <NUM> which is formed of Ni and has the thickness of <NUM> is provided on the surface of lead frame <NUM> was prepared.

Next, solder alloy <NUM> having the thickness of <NUM> is placed on plated layer <NUM> formed of Ni of the prepared circuit board <NUM>, semiconductor device <NUM> is installed on solder alloy <NUM> such that solder alloy <NUM> is in contact with metallized layer <NUM> formed of Ni, and then heating was performed from room temperature to <NUM> while increasing the temperature by <NUM> per minute. Bonded structure <NUM> was manufactured by performing cooling from <NUM> to room temperature while decreasing the temperature by <NUM> per minute after holding at <NUM> for one minute.

A heat cycle test was performed on bonded structures <NUM> of Examples and Comparative Examples <NUM>-<NUM> to <NUM> - <NUM> so as to evaluate the crack resistance. In the heat cycle test, a cycle of -<NUM> and <NUM> for <NUM> minutes was set as one cycle using a liquid tank test tank, and <NUM> cycles of tests were performed. The sample after the test was observed with an ultrasonic microscope and a peeled-off area was divided by a bonded area so as to calculate the crack rate. When the crack rate exceeds <NUM>%, the heat generation of the silicon chip cannot be efficiently released to the lead frame. Thus if the crack rate is equal to or less than <NUM>%, it is determined as "good", and if the crack rate is more than <NUM>%, it is determined as "poor".

The measurement results of the crack rate (%) and the determination result in the heat cycle test are also indicated in Tables <NUM> to <NUM>.

Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and Comparative Example <NUM>-<NUM> are different from Comparative Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> in which the content of Sb is <NUM> wt% from the aspect that the content of Sb is <NUM> wt%. The crack rates of Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and Comparative Example <NUM>-<NUM> were <NUM>%, <NUM>%, <NUM>%, and <NUM>%, and thus the determination was "good". In contrast, the crack rates of Comparative Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> were <NUM>%, <NUM>%, <NUM>%, <NUM>% and thus the determination was "poor".

Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and Comparative Example <NUM>-<NUM> are different from Comparative Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> in which the content of Sb is <NUM> wt% from the aspect that the content of Sb is <NUM> wt%. The crack rates of Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and Comparative Example <NUM>-<NUM> were <NUM>%, <NUM>%, <NUM>%, and <NUM>%, and thus the determination was "good". In contrast, the crack rates of Comparative Examples2-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> were <NUM>%, <NUM>%, <NUM>%, and <NUM>%, and thus the determination was "poor".

From this result, it was found that crack resistance is enhanced when Sb is in a range of <NUM> wt% to <NUM> wt%. The reason for this is inferred that when the SnSb compound exhibits the effect of dispersion strength, if the content of Sb is small, the effect cannot be obtained; whereas if the content of Sb is large, the strength is improved, but the ductility of the solder alloy is deteriorated, so that the crack resistance is deteriorated.

In all of Examples, , the content of Sb was in a range of <NUM> wt% to <NUM> wt%, the content of Te was in a range of <NUM> wt% to <NUM> wt%, and the content of Au was in a range of <NUM> wt% to <NUM> wt%. In all of Examples, the crack rate is lower than <NUM>%, the result was "good" and a good result was obtained.

Even when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, in a case where the content of Te is equal to or less than <NUM> wt% as in Comparative Examples <NUM>-<NUM> to <NUM>, the crack rate is equal to or higher than <NUM>%, and thereby the determination was "poor".

Even when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, in a case where the content of Au is equal to or less than <NUM> wt% as in Comparative Examples <NUM>-<NUM> to <NUM>, the crack rate is equal to or higher than <NUM>%, and thereby the determination was "poor".

Even when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, in a case where the content of Au is equal to or more than <NUM> wt% as in Comparative Examples <NUM>-<NUM> to <NUM>, the crack rate is equal to or higher than <NUM>%, and thereby the determination was "poor".

On the basis of the above results, it was found that when the content of Te is in a range of <NUM> wt% to <NUM> wt%, and the content of Au is in a range of <NUM> wt% to <NUM> wt%, the crack resistance of the solder material can be effectively enhanced. The reason for this is inferred that when the Te content is equal to or more than <NUM> wt%, the effect of solid solution of Te is effectively obtained, and when the content of Te is equal to or less than <NUM> wt%, precipitation of Te as a compound is suppressed, and thus the ductility was improved so that the crack resistance was enhanced. In addition, when the content of Au is equal to or more than <NUM> wt%, Au having a different ionic radius from Te can be effectively substituted with Te which is solidly solved in Sn such that dislocations are effectively generated, and thereby the elongation high temperature is improved and the crack resistance is enhanced as well. On the other hand, it is presumed that when the content of Au is equal to or less than <NUM> wt%, the precipitation of a brittle compound containing Au and Sn can be suppressed, and thereby the crack resistance is improved.

Even when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, and the content of Te is in a range of <NUM> wt% to <NUM> wt%, and the content of Au is in a range of <NUM> wt% to <NUM> wt%, in a case where the content of Ag is equal to or less than <NUM> wt% as indicated in Comparative Example <NUM>-<NUM>, and the content of Ag is equal to or more than <NUM> wt% as indicated in Comparative Example <NUM>-<NUM>, the crack rate is equal to higher than <NUM>%, and thereby the determination was "poor".

Even when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, and the content of Te is in a range of <NUM> wt% to <NUM> wt%, and the content of Au is in a range of <NUM> wt% to <NUM> wt%, in a case where the content of Cu is equal to or less than <NUM> wt% as indicated in Comparative Example <NUM>-<NUM>, and the content of Cu is equal to or more than <NUM> wt% as indicated in Comparative Example <NUM>-<NUM>, the crack rate is equal to higher than <NUM>%, and thereby the determination was "poor".

In a case where the content of Sb is in a range of <NUM> wt% to <NUM> wt%, the content of Te is in a range of <NUM> wt% to <NUM> wt%, and the content of Au is in a range of <NUM> wt% to <NUM> wt%, and in a case where the total content of Ag and Cu is in a range of <NUM> wt% to <NUM> wt% as indicated in Examples <NUM>-<NUM> to <NUM>-<NUM>, the crack rates in all the cases are lower than <NUM>%, and thus the determination was "good". However, in a case where the total content of Ag and Cu is equal to or less than <NUM> wt%, or equal to or more than <NUM> wt% as indicated in Comparative Examples <NUM>-<NUM> to <NUM>-<NUM>, the crack rate was equal to or more than <NUM>%.

On the basis of the above results, it was found that when total content of Ag and Cu is in a range of <NUM> wt% to <NUM> wt%, the crack resistance of the solder material can be effectively enhanced. The reason for this is considered that when the total content of Ag and Cu is equal to or more than <NUM> wt%, at least one of the intermetallic compound of Sn and Au and the intermetallic compound of Sn and Cu is precipitated at a constant amount, and thereby the strength is improved. Also, it is considered that when the total content of Ag and Cu is equal to or less than <NUM> wt%, the amount of intermetallic compound with Sn is not excessively large, and a certain amount of Te and Au are solidly dissolved in Sn, and therefore, the improvement of elongation, which is the effect of the solid solution, was effectively obtained. With this, it is considered that the stress at the time of the heat cycle can be absorbed and thereby the crack resistance is enhanced.

On the basis of the above results, it was found that when the content of Sb is in a range of <NUM> wt% to <NUM> wt%, the content of Te is in a range of <NUM> wt% to <NUM> wt%, the content of Au is in a range of <NUM> wt% to <NUM> wt%, the content of Ag is in a range of <NUM> wt% to <NUM> wt%, the content Cu is equal to or greater than <NUM> wt% and less than <NUM> wt%, and the total content of Ag and Cu is in a range of <NUM> wt% to <NUM> wt%, the crack resistance is enhanced. However, Comparative Examples <NUM>-<NUM> to <NUM>-<NUM> are not included in the present invention.

As indicated in Table <NUM>, the solder alloys <NUM> in Examples <NUM>-<NUM> to <NUM>-<NUM>, which contain different contents of Sb, Te, Au, Ag, and Cu, and the balance of Sn, were prepared, and bonded structure <NUM> was manufactured by using each of prepared solder alloys <NUM>. After the bonded structures <NUM> having the solder alloys <NUM> in Examples <NUM>-<NUM> to <NUM>-<NUM> were all manufactured by using the same method as that in Example <NUM>-<NUM>, the same heat cycle test was performed, and then the measurement and determination of the crack rate (%) were performed. The measurement results and determination are indicated in Table <NUM>.

In Examples <NUM>-<NUM> to <NUM>-<NUM>, the content of Cu was equal to or greater than <NUM> wt% and less than <NUM> wt%.

In addition, in Examples <NUM>-<NUM> to <NUM>-<NUM>, the content of Ag was equal to or greater than <NUM> wt% and less than <NUM> wt%, and the content of Cu was equal to or greater than <NUM> wt% and less than <NUM> wt%.

From these results, it was found that all of the crack rates were evaluated as "good", and the content of Cu was greater than <NUM> wt% and less than <NUM> wt%, the crack rate was likely to be the lowest, and the crack resistance was improved.

Accordingly, among the solder in which the content of Sb is in a range of <NUM> wt% to <NUM> wt%, the content of Te is in a range of <NUM> wt% to <NUM> wt%, the content of Au is in a range of <NUM> wt% to <NUM> wt%, the content of Ag is in a range of <NUM> wt% to <NUM> wt%, the content Cu is equal to or greater than <NUM> wt% and less than <NUM> wt%, and the content of the sum of Ag and Cu is in a range of <NUM> wt% to <NUM> wt%, high reliability of the bonded structure can be realized by using a solder alloy with high crack resistance.

The solder alloy of the disclosure and the bonded structure using the same were manufactured as follows.

Solder alloy <NUM>, semiconductor device <NUM>, and circuit board <NUM> were prepared. First, an alloy containing <NUM> wt% of Sb, <NUM> wt% of Te, <NUM> wt% of Ag, and the balance of Sn was formed into a sheet shape having a thickness of <NUM> so as to obtain solder alloy <NUM>. Then, both surfaces of solder alloy <NUM> formed into the sheet shape were coated with an Au film having the thickness of <NUM> such that the content of Au of solder alloy <NUM> was <NUM> wt% when solder alloy <NUM> is melted and mixed with the entire Au film on the both surfaces. In the composition ratio of solder alloy <NUM> melted and mixed with the Au plating, Sb was <NUM> wt%, Te was <NUM> wt%, Au was <NUM> wt%, Ag was <NUM> wt%, and the balance was Sn.

Solder alloy <NUM> having the thickness of <NUM> is placed on plated layer <NUM> formed of Ni of the prepared circuit board <NUM>, semiconductor device <NUM> is installed on solder alloy <NUM> such that solder alloy <NUM> is in contact with metallized layer <NUM> formed of Ni, and then heating was performed from room temperature to <NUM> while increasing the temperature by <NUM> per minute. Bonded structure <NUM> was manufactured by performing cooling from <NUM> to room temperature while decreasing the temperature by <NUM> per minute after holding at <NUM> for one minute.

The manufactured bonded structure was subjected to the same heat cycle test as that of Example <NUM> so as to determine the crack resistance. As a result, the crack rate after the heat cycle test of Example <NUM>-<NUM> was <NUM>%, and the determination was "good".

In Example <NUM>-<NUM>, the Au plating was performed on the solder alloy containing Sn, Sb, Te, and Ag. In this case, the composition ratio of Au in solder alloy <NUM> is <NUM> wt%, and due to the heat at the time of bonding, Au is diffused into the solder bonded layer, and thereby substantially the same bonded structure as that of Example <NUM>-<NUM> is formed.

In the mounting structure (Example <NUM>-<NUM>) manufactured under the same conditions as in Example <NUM>-<NUM> except that <NUM> wt% of Cu was contained instead of Ag, the crack rate was <NUM>%, and thus a good result was obtained. In the mounting structure (Example <NUM>-<NUM>) manufactured under the same conditions as in Example <NUM>-<NUM> except that <NUM> wt% each of Cu and Ag were contained, the crack rate was <NUM>%, and thus a good result was obtained.

In the mounting structure (Example <NUM>-<NUM>) manufactured under the same conditions as in Example <NUM>-<NUM> except that <NUM> wt% of Cu was contained instead of Ag, the crack rate was <NUM>%, and thus a good result was obtained.

In the mounting structure (Example <NUM>-<NUM>) manufactured under the same conditions as in Example <NUM>-<NUM> except that <NUM> wt% of Ag and <NUM> wt% of Cu were contained, the crack rate was <NUM>%, and thus a good result was obtained.

Examples <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> are Reference Examples.

It was clearly found that Au may be formed on the surface of the solder alloy as long as it is within the composition range of the disclosure.

Claim 1:
A solder alloy comprising:
Sb of which a content is in a range of <NUM> wt% to <NUM> wt%;
Te of which a content is in a range of <NUM> wt% to <NUM> wt%;
Au of which a content is in a range of <NUM> wt% to <NUM> wt%,
at least one of Ag and Cu, wherein
a content of Ag in the solder alloy is in a range of <NUM> wt% to <NUM> wt%;
a content of Cu is equal to or greater than <NUM> wt% and less than <NUM> wt%;
a content of a sum of Ag and Cu in the solder alloy is in a range of <NUM> wt% to <NUM> wt%; and
a balance of Sn.