JP2017035708A - Sb-Cu SOLDER ALLOY CONTAINING NO Pb - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-temperature solder alloy having a solidus temperature of 540°C or lower suited for use in the assembly of an electronic component, excellent in not only bondability but also workability and reliability and far more inexpensive than Au solder.SOLUTION: An Sb-Cu solder alloy containing no Pb has a Cu content of 11.0 mass % to 38.0 mass%, and the remainder being Sb and an inevitable impurity. This Pb-free Sb-Cu solder alloy may further contain at least one kind of Ag, Al, Ge, In, Mg, Ni, Sn, Zn and P individually within individually predetermined content ranges.SELECTED DRAWING: None

Description

  The present invention relates to a so-called Pb-free solder alloy containing no Pb, and more particularly to a Pb-free Sb—Cu solder alloy suitable for high temperature use.

  High-temperature soldering is performed in soldering in the assembly process of various electronic components including die bonding of power transistor elements. At that time, a solder alloy having a relatively high melting point of about 300 to 400 ° C. , Also referred to as “high temperature solder alloy”). As such a high-temperature solder alloy, a Pb-based solder alloy represented by a Pb-5 mass% Sn alloy has been mainly used conventionally. However, in recent years, there has been a strong movement to limit the use of Pb due to consideration for environmental pollution. For example, Pb is a regulated substance in the RoHS directive. Corresponding to such movement, in the field of assembling electronic components and the like, soldering using a Pb-free (lead-free) solder alloy, that is, a Pb-free solder alloy is required.

  In response to such a demand, a Pb-free solder alloy containing Sn as a main component has already been put to practical use as a solder alloy for medium and low temperatures (about 140 to 230 ° C.). For example, in Patent Document 1, Sn is the main component, Ag is 1.0 to 4.0 mass%, Cu is 2.0 mass% or less, Ni is 0.5 mass% or less, and P is 0.2 mass%. Pb-free solder alloys containing up to 10% are described. Patent Document 2 describes a Pb-free solder alloy containing 0.5 to 3.5% by mass of Ag, 0.5 to 2.0% by mass of Cu, and the balance being Sn. On the other hand, examples of high temperature Pb-free solder alloys include Au—Sn solder alloys and Au—Ge solder alloys. However, since these are based on Au, they are very expensive and are not used except for very limited applications such as optical device elements that require high reliability. Is rarely used.

  Therefore, Bi-based solder alloys and Zn-based solder alloys have been researched and developed in order to realize Pb-free even in relatively inexpensive high-temperature solder alloys used for general electronic components and the like. For example, for Bi-based solder alloys, Patent Document 3 discloses a Bi / Ag-based brazing material containing 30 to 80% by mass of Bi and having a melting temperature of 350 to 500 ° C. Patent Document 4 discloses a method for producing a solder alloy that can adjust a liquidus temperature and reduce variations by adding a binary eutectic alloy to a eutectic alloy containing Bi and further adding additional elements. It is disclosed. As for the Zn-based solder alloy, for example, Patent Document 5 describes a high-temperature Zn-based solder alloy based on a Zn-Al alloy in which Al is added to lower the melting point of Zn and Ge or Mg is added thereto. Yes. Patent Document 5 also describes that the addition of Sn or In has an effect of further lowering the melting point.

  Specifically, in Patent Document 5, a Zn alloy containing 1 to 9% by mass of Al and 0.05 to 1% by mass of Ge, with the balance being Zn and inevitable impurities; 5 to 9% by mass of Al, Mg Zn alloy composed of 0.01 to 0.5% by mass with the balance being Zn and inevitable impurities; Al is 1 to 9% by mass, Ge is 0.05 to 1% by mass, Mg is 0.01 to 0.5% Zn alloy containing Zn and the balance consisting of Zn and unavoidable impurities; Al containing 1 to 9% by mass; Ge containing 0.05 to 1% by mass; Sn and / or In containing 0.1 to 25% by mass and the balance being Zn alloy composed of Zn and inevitable impurities; Al 1-9 mass%, Mg 0.01-0.5 mass%, In and / or Sn 0.1-25 mass%, the balance Zn and inevitable impurities Zn alloy comprising: Al 1-9 mass%, Ge 0.05-1 mass%, Mg 0.01-0.5 The amount%, Sn and / or In includes 0.1 to 25 wt%, and the balance are described Zn alloy consisting of Zn and unavoidable impurities.

Japanese Patent Application Laid-Open No. 11-077366 Japanese Patent Laid-Open No. 08-215880 JP 2002-160089 A JP 2006-167790 A Japanese Patent No. 3850135

  Thermoplastic resins and thermosetting resins are often used as materials for general electronic components and substrates. Therefore, the working temperature during soldering is preferably less than 400 ° C, and it is desirable for small-sized SiC semiconductor devices and the like. Even when a high heat-resistant device is used or when joining by laser, 540 ° C. or lower is desirable. However, since the Bi / Ag brazing material of Patent Document 3 described above has a high liquidus temperature of 400 to 700 ° C., it is estimated that the working temperature at the time of joining is 400 to 700 ° C. or higher, It is considered that the temperature is higher than the substrate can withstand. In addition, the method of Patent Document 4 becomes a quaternary or higher multi-component solder alloy only by adjusting the temperature of the liquidus, and Bi is not effectively improved in terms of brittle mechanical properties.

  The Zn-based solder alloy disclosed in Patent Document 5 described above often has insufficient wettability within the composition range. That is, Zn, which is the main component, has a strong reducibility, so that it is easily oxidized by itself, and as a result, the wettability is extremely deteriorated. Moreover, since Al is more reducible than Zn, for example, even when added in an amount of 1% by mass or more, the wettability is greatly reduced. These oxidized Zn and Al cannot be reduced even if Ge or Sn is added, and the wettability cannot be improved.

  As described above, the Zn—Al-based alloy is an alloy that has a melting point of about 300 to 400 ° C. (Zn—Al eutectic temperature: 381 ° C.), but is not preferable from the viewpoint of wettability. Furthermore, when Mg or the like is added to the Zn—Al-based alloy, an intermetallic compound is generated and becomes extremely hard, and there is a problem that good workability may not be obtained. For example, a Zn—Al-based alloy containing 5% by mass or more of Mg cannot be processed into a wire shape or a sheet shape that is difficult to process.

  As described above, with respect to high-temperature Pb-free solder alloys, particularly Pb-free solder alloys mainly composed of Zn, it is a major issue to improve wettability while balancing with various properties such as workability. However, this problem has not been solved yet. Thus, it can be replaced with a conventional high-temperature solder alloy represented by Pb-5 mass% Sn alloy, Au-Sn alloy, Au-Ge alloy, etc., and is a Pb-free and inexpensive high-temperature solder alloy. Is not yet put into practical use.

  The present invention has been made in view of such circumstances, has a solidus temperature of about 540 ° C. or less suitable for use in assembling electronic components, and has excellent bondability, workability, and reliability. Another object of the present invention is to provide a high-temperature solder alloy made of an Sb—Cu-based alloy that is superior to the Au-based solder and is much less expensive than an Au-based solder.

  In order to achieve the above object, the first Pb-free Sb—Cu solder alloy provided by the present invention has a Cu content of 11.0% by mass or more and 38.0% by mass or less, with the balance being Sb and inevitable impurities. It is characterized by comprising.

  Further, the second Pb-free Sb—Cu solder alloy provided by the present invention is the same as the first Pb-free Sb—Cu solder alloy, but Ag, Al, Ge, In, Mg, Ni, Sn, Zn, and When it contains at least one of P and contains Ag, its content is 0.01 mass% or more and 15.0 mass% or less, and when it contains Al, its content is 0.01 mass%. % Or more and 2.0% by mass or less. When Ge is contained, the content is 0.01% by mass or more and 10.0% by mass or less. When In is contained, the content is 0.01% by mass. % Or more and 5.0% by mass or less. When Mg is contained, the content is 0.01% by mass or more and 0.5% by mass or less. When Ni is contained, the content is 0.01% by mass. % Or more and 0.7% by mass or less, and when Sn is contained, its content is 0.01 quality. When Zn is contained, the content is 0.01 mass% or more and 2.0 mass% or less, and when P is contained, the content is 0.500. It is characterized by being not more than mass%.

  According to the present invention, it has a solidus temperature of about 540 ° C. or less suitable for use in the assembly of electronic components, etc., and has excellent bondability, excellent workability and reliability, does not contain Pb, In addition, it is possible to provide a high temperature solder alloy made of an Sb—Cu alloy that is much cheaper than Au solder. This Sb—Cu-based alloy can sufficiently withstand a reflow temperature of about 300 ° C., and the power of Si semiconductor element bonded bodies, SiC semiconductor element bonded bodies, GaN semiconductor element bonded bodies, etc., which are particularly high in operating temperature even in high temperature applications. It can be suitably used for bonding such as die bonding of transistor elements, bonding by laser, and sealing of a crystal resonator.

It is a phase diagram of a Cu-Sb binary system alloy. It is a typical longitudinal cross-sectional view of the joined body by which the solder alloy sample was soldered on Cu substrate which has Ni layer produced for the wettability test. It is a side view which shows the maximum solder height Y used for calculation of the aspect ratio of the joined body of FIG. FIG. 3 is a plan view showing a maximum solder wetting spread length X1 and a minimum solder wetting spread length X2 used for calculating the aspect ratio of the joined body in FIG. 2.

  The first Pb-free Sb—Cu-based solder alloy according to the present invention does not contain Pb, contains Cu as an essential component in an amount of 11.0% by mass to 38.0% by mass, and the remainder is unavoidably included in production. It consists of elements (inevitable impurities) and Sb. Sb and Cu produce a eutectic alloy composed of η phase and Sb solid solution, and the eutectic temperature is 526 ° C. The melting point of Cu is 1085 ° C., the melting point of Sb is 631 ° C., and the melting point can be lowered to 526 ° C. by alloying.

  The solidus temperature of 526 ° C. is relatively high as a high-temperature solder alloy, but having such a high melting point can suppress the softening and strength reduction of the solder alloy even if the temperature rises when using electronic components, Therefore, since high bonding reliability can be obtained, it is suitable as a bonding material for SiC semiconductor elements characterized by high-temperature operation. Further, when sealing, for example, a crystal resonator or a SAW filter by laser bonding, it can be said that it is an excellent material that is very easy to use because it only raises the temperature of the laser irradiated portion and does not adversely affect the peripheral members.

  Further, the second Pb-free Sb—Cu based solder alloy according to the present invention is further made of Ag, Al, Ge, In, Mg, Ni, Sn, Zn and the first Pb free Sb—Cu based solder alloy. In addition, the solidus temperature and the liquidus temperature are decreased by containing at least one of P and P as necessary, and wettability, bondability, workability, reliability, and the like are appropriately adjusted according to usage requirements. It is possible to make adjustments, and the solder material can be made even easier to use.

  Thus, the Sb—Cu based alloy of the present invention is based on the composition of eutectic points (Sb = 76.5 mass%, Cu 23.5 mass%), and Ag, Al, Ge, In, Mg as required. By appropriately containing at least one of Ni, Sn, Zn and P, it is possible to provide a solder alloy satisfying various properties required for solder such as melting point, wettability, bondability, and workability. .

  Note that P is the most suitable element for improving wettability because P is more reducing than Sb and Cu and removes oxygen from the bonding surface and solder as gaseous phosphorus oxide during bonding. Naturally, P can also reduce and remove the surface oxide film of Cu substrate or Ni-plated Cu substrate, so wettability can be achieved without using forming gas (gas containing hydrogen to reduce the oxide film on the substrate) during bonding. Can be improved. Next, each element contained in the above-described Pb-free Sb—Cu solder alloy of the present invention will be described in detail.

<Sb, Cu>
Sb and Cu are elements constituting essential components in the Pb-free Sb—Cu solder alloy of the present invention. As shown in the Cu—Sb binary phase diagram of FIG. 1, Sb and Cu form a eutectic alloy composed of η phase and Sb solid solution, and the eutectic temperature is 526 ° C. The melting point of Cu is 1085 ° C., the melting point of Sb is 631 ° C., and the melting point can be lowered to 526 ° C. by alloying. Furthermore, if various elements described later are contained as necessary, the solidus temperature and the liquidus temperature can be lowered, and the solder material becomes easier to use.

  As described above, since the Sb—Cu based solder alloy of the present invention is based on the composition of eutectic points (Sb = 76.5 mass%, Cu 23.5 mass%), the Cu content is 11.0 mass. % Or more and 38.0% by mass or less. Thus, if the Cu content is in the range of 11.0% by mass or more and 38.0% by mass or less, for SiC semiconductor elements characterized by high-temperature operation utilizing a high melting point of 526 ° C. In addition, it is possible to suppress the softening and strength reduction of the solder alloy even when the electronic component becomes high temperature during use, so that high bonding reliability can be obtained. Further, when sealing, for example, a crystal resonator or a SAW filter by laser bonding, it can be said that it is an easy-to-use and excellent material because the temperature rises only partially during bonding and does not adversely affect the peripheral members.

  On the other hand, when the Cu content is less than 11.0% by mass, the liquidus temperature becomes too high, causing a phenomenon of melting and separation, or the Sb ratio becomes too high and becomes brittle. . On the other hand, if the Cu content exceeds 38.0% by mass, the reaction between the substrate and the solder alloy may be insufficient and the bonding strength may be lowered, or the β phase, ε phase, ζ phase, etc. may be partially As a result, a eutectoid structure begins to appear and a complex crystal structure is formed, and the strength and stress relaxation properties of the solder alloy are extremely reduced.

<Ag, Ge, In>
Ag, Ge, and In are elements that are appropriately contained in order to improve or adjust various properties in the Sb—Cu solder alloy of the present invention, and the main effects obtained by containing these elements are the same. , To improve workability. Ag forms a eutectic alloy of Sb solid solution and ε phase with Sb. And Cu produces | generates the eutectic alloy which consists of Cu solid solution and Ag solid solution. Thus, since Ag forms a eutectic alloy with both Sb and Cu, inclusion of Ag in the Sb—Cu alloy results in a relatively soft alloy and improved workability and stress relaxation.

  When Ag is contained in the Sb—Cu solder alloy, the content is preferably 0.01% by mass or more and 15.0% by mass or less. If the Ag content is less than 0.01% by mass, the content is too small and substantially no effect is exhibited. If the Ag content exceeds 15.0% by mass, the liquidus temperature becomes too high and good bonding cannot be performed. If the content of Ag is 0.3% by mass or more and 8.0% by mass or less, it is preferable because the above-described effect appears more remarkably.

  Ge produces a eutectic alloy composed of Sb solid solution and Ge solid solution. And Cu produces a eutectoid alloy. Since Ge forms eutectic alloys and eutectoid alloys with Sb and Cu in this way, it is possible to improve workability by adding Ge, and further adjust other properties such as strength and melting point in a well-balanced manner. can do. The reason why the addition of Ge makes it possible to adjust not only the workability improvement effect but also various characteristics in this way is that Ge has a property similar to Sb, and thus takes a form of partial replacement. It is.

  When Ge that can provide such an excellent effect is contained in the Sb—Cu based solder alloy, the content is preferably 0.01% by mass or more and 10.0% by mass or less. If the Ge content is less than 0.01% by mass, the content is too small and substantially no effect appears. On the other hand, if it exceeds 10.0% by mass, the content is too high and the liquidus temperature rises too much, or a sufficient bonding layer cannot be formed with the substrate, etc. End up.

  In, Sb forms a eutectic alloy of Sb solid solution and InSb intermetallic compound. Then, several mass% is dissolved in Cu. In this way, In generates a eutectic alloy, and since it originally has a very soft property, it contributes to the improvement of workability and stress relaxation properties. That is, by adding In, the softness is exhibited and the elongation rate and the like are improved, so that the rolling process and the press process are facilitated, and the ability to alleviate the thermal stress is further improved. When In exhibiting such an excellent effect is contained in the Sb—Cu based solder alloy, the content is 0.01 mass% or more and 5.0 mass% or less. If the In content is less than 0.01% by mass, the content is too small, and substantially no effect appears. On the other hand, if it exceeds 5.0% by mass, the ratio of the intermetallic compound is excessively increased, and conversely, the workability is lowered.

<Al, Mg, Sn, Zn>
Al, Mg, Sn, and Zn are elements that are appropriately contained in order to improve or adjust various properties in the Sb—Cu solder alloy of the present invention, and the main effects obtained by containing these elements are the same. And improving wettability. Specifically, Al generates Sb and a high melting point Al—Sb intermetallic compound (melting point: 1063 ° C.). And about 8% by mass is dissolved in Cu. If such an intermetallic compound having a high melting point is produced, tip tilt or melting phenomenon is caused at the time of bonding, so that a large amount of Al cannot be contained in the Sb—Cu alloy.

  Although the effect obtained by containing Al is in improving wettability, Al is a metal that is relatively easily oxidized and is more easily oxidized than Sb and Cu. For this reason, when Al is contained in a small amount, Al forms a thin oxide layer on the solder surface and improves wettability. As already described, a large amount of Al cannot be contained, and the upper limit of the Al content is 2.0% by mass. If the Al content exceeds 2.0% by mass, not only the tip tilt and melting phenomenon occur, but also the oxide layer becomes thicker and the wettability is reduced. On the other hand, the lower limit of the Al content is 0.01% by mass. If the Al content is less than 0.01% by mass, the content is too small and substantially no effect appears.

Mg hardly dissolves in Sb and forms a eutectic alloy having a relatively high melting point Mg ₃ Sb ₂ intermetallic compound (melting point: 621 ° C.). Then, several mass% is dissolved in Cu. If Mg is contained in a large amount in the same manner as Al, an intermetallic compound having a high melting point is generated in an allowable amount or more, causing tip tilt and the like, so that it cannot be contained in a large amount in an Sb—Cu alloy. Since Mg is an element having a stronger reducibility than Al, a thin oxide layer can be formed in a smaller amount than Al, and wettability can be improved. For this reason, when Mg is contained in the Sb—Cu solder alloy, the content is preferably 0.01% by mass or more and 0.5% by mass or less. If the Mg content is less than 0.01% by mass, the content is too small and substantially no effect appears. On the other hand, if the Mg content exceeds 0.5% by mass, tip tilt and wettability are reduced.

Sn is a solid solution of several mass% in Sb and a little solid solution in Cu. As described above, Sn dissolves in Sb and Cu, but does not adversely affect the mechanical characteristics and the like. Since Sn is rich in reactivity with Cu, Ni and the like, an intermetallic compound such as Cu ₃ Sn is generated at the interface with the substrate and the like, thereby realizing strong bonding. That is, by adding Sn to the Sb—Cu-based alloy, the wettability and the bondability can be improved, so that the characteristics of the solder can be improved.

  Thus, when Sn which has the effect of improving various properties of the solder alloy is contained in the Sb—Cu-based alloy, the content is preferably 0.01% by mass or more and 3.0% by mass or less. If the Sn content is less than 0.01% by mass, the content is too small and substantially no effect appears. On the other hand, when Sn content exceeds 3.0 mass%, the intermetallic compound layer produced | generated in a joining interface will become thick, and there exists a possibility that a solder may become hard and stress relaxation property may be reduced.

  Zn hardly dissolves in Sb, and forms a eutectic alloy of Sb solid solution and SbZn intermetallic compound. Zn can be improved in wettability by being contained in a small amount in the Sb—Cu alloy, but if it is contained in a large amount, the proportion of the SbZn intermetallic compound becomes too high and the workability and the like are lowered. The reason why Zn improves wettability is the high reactivity of Zn. Specifically, it has excellent reactivity with Cu and Ni, so that wettability and bondability are improved. Furthermore, since Zn is more easily oxidized than Sb and Cu, a thin oxide layer is formed with a small amount of addition and wettability is improved.

  When Zn is contained in the Sb—Cu-based alloy, the content is preferably 0.01% by mass or more and 2.0% by mass or less. If the Zn content is less than 0.01% by mass, the content is too small and substantially no effect appears. If the Zn content exceeds 2.0% by mass, the ratio of the metal compound increases, and the workability and stress relaxation properties decrease, and the oxide layer becomes thick, leading to a decrease in wettability.

<Ni>
Ni is an element contained as appropriate in order to improve or adjust various properties in the Sb-Cu solder alloy of the present invention, and the main effect obtained by including Ni is to improve workability and stress relaxation. However, the mechanism is fundamentally different from Ag and the like described above. That is, Ni has a very high melting point of 1455 ° C., and when the solder is melted and solidified, it first precipitates, and fine crystals grow using it as a nucleus, so that the structure becomes a fine crystal structure. The progress of cracks is easily stopped at the grain boundaries. As a result, even if various stresses are applied to the solder, it is difficult for the cracks to progress, and even if the sheet material is processed, the occurrence of defects such as cracks can be suppressed, and the joining reliability and the like are dramatically improved.

  Since Ni exhibits the effect of improving workability by the above-described mechanism, it is not preferable to increase the Ni content too much. If the Ni content is too large, the density of Ni nuclei increases, the crystal grains become too large without being refined, and the Ni addition effect is halved. Therefore, the upper limit when Ni is contained is set to 0.7 mass%. On the other hand, the lower limit is 0.01% by mass. If the lower limit is not reached, the precipitation of nuclei is too small to substantially improve the workability.

<P>
P is an element to be included as necessary when there is a characteristic to be further improved in the Pb-free Sb—Cu solder alloy of the present invention, and the main effect obtained by the addition is an improvement in wettability. The mechanism by which P improves wettability is as follows. That is, P is highly reducible and suppresses oxidation of the solder alloy surface by oxidizing itself. When sufficient wettability cannot be ensured when using a solder alloy for sealing a crystal resonator that requires extremely high wettability, the role of improving wettability by containing P is significant.

  In addition, the inclusion of P also has the effect of reducing the generation of voids during bonding. That is, as already described, since P is easily oxidized by itself, oxidation proceeds preferentially over Sb and Cu, which are the main components of the solder alloy, at the time of joining. It is possible to ensure wettability by reducing the joint surfaces of components and the like. In this joining, since solder and oxides on the surface of the joining surface disappear, gaps (voids) formed by the oxide film are hardly generated, and the joining property, reliability, and the like can be improved. Note that P is not left on the surface of the solder, the substrate or the like because it vaporizes and flows to the atmosphere gas when the solder alloy such as Sb or Cu or the substrate is reduced to become an oxide. For this reason, there is no possibility that the residue of P adversely affects reliability and the like, and P can be said to be an excellent element from this point.

  When P is contained in the Sb—Cu-based solder alloy, the content is set to 0.500% by mass or less. Since P is very reducible, the effect of improving wettability can be obtained if it is contained even in a trace amount. However, the effect of improving the wettability does not change much even if the content exceeds 0.50% by mass, and excessive amounts of P and P oxide gases are generated and the void ratio is increased. May form a fragile phase and segregate, embrittle the solder joint and reduce reliability. In particular, it has been confirmed that wire breakage tends to be caused when processing into a shape such as a wire. In addition, if content of P is 0.300 mass% or less, since the above-mentioned effect appears more notably, it is preferable.

  Sb, Cu, Ag, Al, Ge, In, Mg, Ni, Sn, Zn, P, and Au, each having a purity of 99.9% by mass or more, were prepared as raw materials. Large flakes and bulk-shaped raw materials were reduced to a size of 3 mm or less by cutting and crushing while paying attention to ensure that the alloy after melting did not vary in composition depending on the sampling location. Next, a predetermined amount of each of these raw materials was weighed and placed in a graphite crucible for a high-frequency melting furnace.

  The crucible containing the raw materials was placed in a high-frequency melting furnace, and nitrogen gas was flowed at a flow rate of 0.7 liter / min or more per kg of the raw materials in order to suppress oxidation. In this state, the melting furnace was turned on to heat and melt the raw material. When the metal began to melt, it was stirred well with a mixing rod and mixed uniformly so as not to cause local compositional variations. After confirming sufficient melting, the high frequency power supply was turned off, the crucible was quickly taken out, and the molten metal in the crucible was poured into the mold of the solder mother alloy. For molds, a cylindrical ingot having a diameter of 24 mm × 80 mm in length can be obtained for ball production, and a plate-shaped ingot having a thickness of 5 mm × width of 46 mm × length of 240 mm can be obtained for the production of punched products. used. In this way, two types of Pb-free Sb—Cu-based solder mother alloy ingots of samples 1 to 40 having different mixing ratios of the above-described various raw materials (ie, cylindrical and plate-like ingots) were prepared. . The composition of the obtained solder mother alloys of Samples 1 to 40 was subjected to composition analysis using an ICP emission spectroscopic analyzer (SHIMAZU S-8100). The composition analysis results are shown in Table 1 below.

  Next, the plate-like ingots of Samples 1 to 40 were processed into punched products using a rolling mill and a press. And workability was evaluated by the yield of the obtained punched product. On the other hand, the cylindrical ingots of Samples 1 to 40 were processed into balls using a submerged atomizer. As the liquid at that time, oil having a large effect of suppressing the oxidation of the solder alloy was used. Hereinafter, the processing method of these ribbon-shaped solder alloys and ball-shaped solder alloys and various evaluations performed using these solder alloys will be specifically described.

<Ribbon solder alloy processing method>
First, a plate-like solder mother alloy sample having a thickness of 5 mm, a width of 46 mm, and a length of 240 mm prepared by the above-described method was rolled with a warm rolling mill. The rolling conditions were the same for all samples. That is, the number of rolling was 5 times, the rolling speed was 15 to 30 cm / second, the roll temperature was 290 ° C., and rolling was performed to 59.0 ± 1.0 μm by 5 times of rolling. In this way, a ribbon-shaped solder alloy sample was produced.

<Evaluation of workability (yield of punched product)>
Next, the ribbon-shaped solder alloy sample produced above was punched with a press to produce a punched product, and the workability was evaluated by the punching yield (good product rate) at that time. Specifically, first, each ribbon-shaped solder alloy sample was set in a press machine and punched into a 0.7 mm × 0.3 mm rectangle while supplying lubricating oil. 1000 pieces were punched out for each solder alloy sample. The obtained punched product was collected in a container containing an organic solvent, washed with the organic solvent, and then dried for 2 hours while evacuating with a vacuum dryer. The punched product thus produced was confirmed, and a case where cracks, burrs, burrs, warpage, and the like were found to be defective, and a case where there was no such product and punched into a clean rectangle was evaluated as a good product. Then, the number of non-defective products was divided by the number of punching (1000) and multiplied by 100 to calculate the punching yield (%).

<Processing method for ball-shaped solder alloy>
A cylindrical solder mother alloy sample having a diameter of 24 mm and a length of 80 mm prepared by the above method was put into a nozzle of a submerged atomizer, and the nozzle was heated at 380 ° C. above the quartz tube containing oil (high-frequency dissolution). Set in the coil). The mother alloy in the nozzle was heated to 500 ° C. by high frequency and held for 3 minutes, and then pressure was applied to the nozzle with an inert gas to perform atomization, thereby producing a ball-shaped solder alloy. The inner diameter of the nozzle tip was adjusted in advance so that the ball diameter would be a set value of 0.30 mm. The obtained ball-shaped solder was classified and a ball having a diameter of 0.30 ± 0.015 mm was taken out and used for various evaluations.

  For each of the ball-shaped solder alloys of Samples 1 to 40 described above, after bonding to the substrate as shown below, the aspect ratio of the solder after bonding is measured to evaluate the wettability, and the void ratio is measured. Bondability was evaluated. Furthermore, the heat cycle test was done using the joined body of the board | substrate and solder obtained by the said joining test, and reliability was evaluated. Table 2 shows the results of the obtained aspect ratio (wetability evaluation), void ratio (bondability evaluation), and heat cycle test (reliability evaluation).

<Evaluation of wettability (measurement of aspect ratio)>
A wettability tester (device name: atmosphere control type wettability tester) was started, a double cover was applied to the heater part to be heated, and nitrogen gas was allowed to flow from four locations around the heater part at a flow rate of 12 L / min. . Thereafter, the heater was set to a temperature higher than the melting point by 50 ° C. and heated. After the heater temperature is stabilized at the above set value, a Cu substrate (plate thickness: 0.3 mm) plated with Ni (film thickness: 3.0 μm) is set in the heater section and heated for 25 seconds, and then each sample ball The solder alloy was placed on a Cu substrate and heated for 25 seconds. After heating is completed, the Cu substrate to which the ball-shaped solder alloy is bonded is picked up from the heater section, once installed and cooled in a place where the nitrogen atmosphere is maintained next to it, cooled sufficiently, and taken out to the atmosphere It was.

  A bonded body in which the solder alloy 3 was bonded to the Ni layer 2 of the Cu substrate 1 as shown in FIG. 2 was obtained. The aspect ratio of the solder alloy 3 was determined for this joined body. Specifically, the maximum solder height Y shown in FIG. 3, the maximum solder wetting spread length X1 and the minimum solder wetting spread length X2 shown in FIG. 4 were measured, and the aspect ratio was calculated by the following calculation formula 2. It can be determined that the higher the aspect ratio, the thinner the joined solder and the wider the area, and the better the wettability.

[Calculation Formula 2]
Aspect ratio = [(X1 + X2) ÷ 2] ÷ Y

<Evaluation of bondability (measurement of void fraction)>
With respect to the joined body of each sample as shown in FIG. 2 obtained in the same manner as in the evaluation of the wettability, the void ratio of the Cu substrate to which the solder alloy is joined is determined by an X-ray transmission device (manufactured by Toshiba Corporation, Measured using TOSCMICRON-6125). Specifically, X-rays were transmitted vertically from the top to the joint surface between the solder alloy and the Cu substrate, and the void ratio was calculated using the following formula 3.

[Calculation Formula 3]
Void ratio (%) = void area / (void area + joint area between solder alloy and Cu substrate) × 100

<Reliability evaluation (heat cycle test)>
Two bonded bodies as shown in FIG. 2 obtained in the same manner as in the evaluation of the wettability were prepared for each sample, and one of them was cooled at −40 ° C. and 250 ° C. The heat cycle test with 1 cycle of heating was repeated 300 cycles for confirmation on the way, and the remaining one was repeated 500 cycles. Then, the bonded body after completion of the heat cycle test was embedded in the resin, cross-sectional polishing was performed, and the bonded surface was observed with SEM (S-4800, manufactured by Hitachi, Ltd.). The case where there was peeling on the joint surface or a crack in the solder alloy was evaluated as “X”, and the case where there was no such defect and the same joint surface as in the initial state was evaluated as “◯”.

  As can be seen from the results in Table 2, the solder alloys of Samples 1 to 25 that satisfy the requirements of the present invention exhibit good characteristics in all evaluation items. That is, the punching yield, which is an evaluation of workability, is high. Sample 39 (Au-12.5 mass% Ge) and Sample 40 (Au-20 mass% Sn) of comparative examples currently used as Au-based solder Even in comparison, the yield was high. Further, all of the aspect ratios were 6 or more, the solder was thin and spread widely and had good wettability. The highest void ratio was 0.2%, indicating good bondability. In the heat cycle test, no defect appeared even after 500 cycles, and high reliability was shown.

  On the other hand, the solder alloys of samples 26 to 38 as comparative examples (excluding samples 39 and 40 among the comparative examples) had undesirable results in at least any of the characteristics. That is, even if the punching yield is high, it is 62%, which is lower than any of the samples 1-25 satisfying the requirements of the present invention, and the void ratio is 2.8-7.3%, which satisfies the requirements of the present invention. Obviously worse than any of the. In addition, all the aspect ratios were 4.0 or less, and in the heat cycle test, defects occurred in all samples up to 300 times. In addition, it is clear that the solder alloys of Samples 1 to 25 of the present invention are very inexpensive because they do not contain Au, and can be said to be highly practical solder alloys.

1 Cu substrate 2 Ni layer 3 Solder alloy

Claims (4)

  A Pb-free Sb—Cu solder alloy, characterized in that the Cu content is 11.0 mass% or more and 38.0 mass% or less, and the balance is made of Sb and inevitable impurities.   It further contains at least one of Ag, Al, Ge, In, Mg, Ni, Sn, Zn and P, and when it contains Ag, its content is 0.01 mass% or more and 15.0 mass% or less. In the case where Al is contained, the content is 0.01% by mass or more and 2.0% by mass or less, and in the case where Ge is contained, the content is 0.01% by mass or more and 10.0% by mass or less. In the case of containing In, the content is 0.01 mass% or more and 5.0 mass% or less, and in the case of containing Mg, the content is 0.01 mass% or more and 0.5 mass% or less. In the case where Ni is contained, the content is 0.01 mass% or more and 0.7 mass% or less, and in the case where Sn is contained, the content is 0.01 mass% or more and 3.0 mass% or less. In the case where Zn is contained, the content is 0.01 mass% or more and 2.0 mass% or less, and P is contained. 2. The Pb-free Sb—Cu solder alloy according to claim 1, wherein the content thereof is 0.500 mass% or less.   A bonded body characterized by being bonded using the Pb-free Sb-Cu-based solder alloy according to claim 1 or 2. 3. A crystal resonator sealed body, which is sealed using the Pb-free Sb—Cu solder alloy according to claim 1.

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