JP5979083B2 - Pb-free Au-Ge-Sn solder alloy - Google Patents

Description

  The present invention relates to an Au—Ge—Sn based solder alloy that does not contain Pb and contains Au as a main component.

  In recent years, regulations on chemical substances harmful to the environment have become stricter, and this regulation is no exception for solder materials used for the purpose of joining electronic components to a substrate. Lead (Pb) has been used as a main component for solder materials for a long time, but lead has already been a regulated substance under the Rohs Directive. For this reason, development of solder containing no lead (hereinafter referred to as lead-free solder or lead-free solder) has been actively conducted.

  Solder used when bonding a semiconductor element to a substrate is roughly classified into a high temperature (about 260 ° C. to 400 ° C.) and a medium / low temperature (about 140 ° C. to 230 ° C.) depending on the use limit temperature. Regarding solder for solder, lead-free solder has been put into practical use with Sn as a main component. For example, in Patent Document 1, Sn is the main component, Ag is 1.0 to 4.0% by weight, Cu is 2.0% by weight or less, Ni is 0.5% by weight or less, and P is 0.2% by weight. The following lead-free solder alloy composition is described. Patent Document 2 contains 0.5 to 3.5% by weight of Ag, 0.5 to 2.0% by weight of Cu, and the balance is Sn. A lead-free solder of composition is described.

  On the other hand, research and development has been conducted on various high-temperature Pb-free solders. For example, Patent Document 3 discloses a Bi / Ag 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 solder alloy in which a binary Kyochang alloy is added to a Bi-containing alloy containing Bi and an additional element is further added. This solder alloy is a multi-component solder of a quaternary system or higher. However, it has been shown that the liquidus temperature can be adjusted and variations can be reduced.

  As an expensive high-temperature Pb-free solder material, an Au—Sn alloy, an Au—Ge alloy, or the like has already been used in a crystal device, a SAW filter, a MEMS (microelectromechanical system), or the like. For example, in Patent Document 5, Au—Ge, Au—Sb, or Au—Si plate-like low melting point Au alloy brazing is preheated, and then the material is sequentially sent to a press die provided with a heat insulation section. It describes a pressing method for a plate-shaped low melting point Au alloy brazing, characterized in that pressing is performed in a temperature range of from 0C to 350C.

  Patent Document 6 discloses a brazing material used for brazing an external lead of a semiconductor package, and Ag is 10 to 35 wt%, and at least one of In, Ge and Ga is 3 to 15 wt% in total, In addition, the electromigration-preventing brazing material is characterized in that it is an Au alloy composed of the balance Au and the time until short-circuiting in the electromigration test is 1.5 hours or more.

  Further, Patent Document 7 describes a ternary alloy brazing material containing Au / Ge / Sn, where Ts is a temperature at which the liquid phase starts to be generated and Tl is a temperature at which the liquid phase is completely formed. It describes a brazing material characterized by <50 degrees. And according to this patent document 7, while realizing Pb-free, it does not melt at the reflow temperature, and the temperature for joining is too high, so that it does not damage the adhesive or the component itself. It is said that brazing material can be provided.

Japanese Patent Laid-Open No. 1999-077366 Japanese Patent Laid-Open No. 08-215880 JP 2002-160089 A JP 2008-161913 Japanese Patent Laid-Open No. 03-204191 Japanese Patent Laid-Open No. 03-138096 JP 2007-160340 A

  Regarding Pb-free solder materials for high temperatures, there are various reports or proposals other than the above-mentioned patent documents, but a low-cost and versatile solder material has not yet been found. That is, in general, a material having a relatively low heat-resistant temperature such as a thermoplastic resin or a thermosetting resin is frequently used for a semiconductor element or a substrate. Therefore, the working temperature at the time of bonding is less than 400 ° C., preferably 370 ° C. There is a demand to make it below. However, for example, in the Bi / Ag brazing material disclosed in Patent Document 3, since the liquidus temperature is as high as 400 to 700 ° C., it is estimated that the working temperature at the time of joining is also 400 to 700 ° C. or more and is joined. This would exceed the heat resistance temperature of the semiconductor element or substrate.

  In addition, although Au—Sn solder and Au—Ge solder have been put to practical use as expensive Au solders, these Au solders use a large amount of extremely expensive Au. It is very expensive compared to Sn solder. Therefore, it is mainly used only for soldering a portion requiring particularly high reliability, such as a crystal device, a SAW filter, and a MEMS.

  In addition, Au-based solder is very hard and difficult to process. For example, it is necessary to use a special material that does not easily wrinkle the roll or take a long time to roll into a sheet shape. Therefore, extra costs are incurred. Even during press molding, the Au-based solder is hard and brittle, so cracks and burrs are likely to occur, and the yield is much lower than other solders. There is a similar serious problem when processing into a wire shape. Even if an extruder with a very high pressure is used, the extrusion speed cannot be increased because it is hard, and it is about 1 / 100th of Pb solder. There is only productivity.

  In order to deal with various problems of Au solder including the above problems, the techniques described in Patent Documents 5 to 7 have been proposed. However, the technique of Patent Document 5 has the following problems. That is, the material characteristics of a plate-like (sheet-like) low melting point Au alloy brazing material such as Au—Ge, Au—Sb, and Au—Si are brittle like glass plates at room temperature and generally have a directionality. The plane parallel to the longitudinal direction is liable to break even with a slight bending, and has a drawback that the propagation of cracks easily proceeds.

  Therefore, press working has conventionally been performed using a compound mold. However, in this compound mold technology, there is a problem of mold accuracy and a problem of mold life. A technology is disclosed in which materials are sequentially sent to a provided press die and pressed in a temperature range of 100 to 350 ° C. However, there are many problems even in such warm press working.

  That is, in the warm press, the oxidation of the solder alloy proceeds. Therefore, even if the solder contains a large amount of Au, Au-based solder containing other metals such as Ge, Sb, or Sn cannot prevent oxidation of these elements and is higher than room temperature. When pressed at a temperature, the surface is oxidized and the wettability is greatly reduced. Furthermore, since the temperature is high, the solder expands compared to the normal temperature, and even if it is devised, the accuracy of the shape cannot be obtained compared to the press at the normal temperature. In addition, since the solder that has become relatively soft is likely to stick to the mold and is pressed in a state where the solder is bent or distorted, burrs and chips are likely to occur.

  Further, in Patent Document 6, as described above, electromigration of an Au alloy containing 10 to 35 wt% of Ag, 3 to 15 wt% in total of at least one of In, Ge, and Ga, with the balance being Au. A preventive brazing material is described. As an effect of these additive elements, electromigration can be prevented by using Au as a main component, and Ag is added in an amount of 10 to 35 wt% in order to obtain brazing strength, and among In, Ge, and Ga It is described that at least one kind is added in a total of 3 to 15 wt% in order to lower the melting point.

  However, the Au alloy described in Patent Document 6 can prevent the occurrence of electromigration and has a strong and stable brazing strength in comparison with an Ag-based brazing material of Ag-28 wt% Cu or Ag-15 wt% Cu. It was developed as a brazing material to be obtained. For this reason, the Ag content is relatively high, the melting point is lowered, and the solder material is easy to use, and the strength and the electromigration preventing effect are sufficient as compared with conventional Au-based alloys such as Au-Ge alloys. Absent.

  Further, the above-mentioned Patent Document 7 describes a ternary alloy brazing material containing Au / Ge / Sn, where Ts is a temperature at which the liquid phase starts to be generated and Tl is a temperature at which the liquid phase is completely formed. -Ts <50 degrees, which describes a brazing material, which realizes Pb-free, does not melt to the reflow temperature, and is too hot for bonding, for example an adhesive In addition, it has been shown that a brazing material suitable for joining electrical / semiconductor elements that does not damage the components themselves can be provided.

  However, the ternary alloy brazing material containing Au / Ge / Sn described in Patent Document 7 has an extremely wide composition range in which the difference between the liquidus temperature and the solidus temperature is less than 50 ° C. Only a brazing material having the same effects and characteristics in such a wide composition range is not obtained. As an easy-to-understand example, when comparing an Au-12.5 mass% Ge alloy (eutectic point composition) and an Au-20 mass% Sn alloy (eutectic point composition) belonging to the above composition range, the characteristics are as follows: Obviously different.

  That is, since Ge is a metalloid, the Au-12.5 mass% Ge alloy is clearly inferior in workability compared to the Au-20 mass% Sn alloy. For example, when rolling, the yield of Au-12.5 mass% Ge is lower due to the occurrence of cracks and the like. Naturally, when a small amount of the third element is contained in these, there is a composition range in which the third element is dissolved and the characteristics do not change greatly. For example, Au-12.5 mass% Ge—Sn alloy and Au— The properties of the 20 mass% Sn-Ge alloy are greatly different.

  Furthermore, when considering the Ge—Sn alloy, the solidus temperature is 231 ° C., and the melting point is too low as a high-temperature solder. Naturally, even when a small amount of Au is dissolved in the Ge—Sn alloy, there is a region where the difference between the liquidus temperature and the solidus temperature defined in the claims of Patent Document 7 is less than 50 ° C. However, the melting point is still too low for high-temperature solder.

  The present invention has been made in view of the above-described conventional circumstances, and is excellent in various properties such as workability, wettability, and stress relaxation properties, and has extremely high reliability such as a crystal device, a SAW filter, and a MEMS. An object of the present invention is to provide an Au—Ge—Sn based solder alloy that can be used sufficiently even in the required bonding, is inexpensive and contains Pb as a main component, and is free from Pb.

In order to achieve the above object, an Au—Ge—Sn solder alloy provided by the present invention is an Au—Ge—Sn solder alloy for a SAW filter or MEMS , and contains 0.01 mass% or more of Ge. .0 mass contains less, and Sn contained less 40.0 mass% or more 32.0% by weight, the balance Ri Do from Au and unavoidable impurities, the difference between the liquidus temperature and the solidus temperature is less than 50 ° C. It is characterized by being.

The Au-Ge-Sn solder alloy for SAW filter or MEMS of the present invention contains 2.0 mass% to 3.5 mass% of Ge, and Sn is 34.0 mass% to 39.0 mass%. % Or less, and the balance is preferably composed of Au and inevitable impurities.

The Au-Ge-Sn solder alloy for SAW filter or MEMS of the present invention has a P content of 100% by mass in total of Ge, Sn and Au in addition to the above Ge, Sn and Au. Ru can contain 0.500 wt% or less.

  Furthermore, the present invention provides a quartz crystal device and a SAW filter sealed using the Au—Ge—Sn solder alloy of the present invention described above.

  According to the present invention, it does not contain lead, has wettability equivalent to that of a conventional Au-based solder, is excellent in various properties such as workability and stress relaxation properties, and is low in price because of low Au content. In addition, it is possible to provide a Pb-free, high-temperature Au—Ge—Sn solder alloy that can be used in places where extremely high reliability is required, such as quartz devices, SAW filters, and MEMS. . Moreover, since the Au—Ge—Sn solder alloy of the present invention is excellent in workability, productivity can be improved and further cost reduction can be realized.

It is an Au-Sn-Ge system phase diagram. It is sectional drawing which shows typically embodiment of the wettability test which soldered the solder alloy on Cu substrate which has Ni layer. It is a side view which shows typically the aspect-ratio measurement state in the wettability test of FIG. It is a top view which shows typically the aspect-ratio measurement state in the wettability test of FIG.

  The composition of the Au—Ge—Sn solder alloy of the present invention basically includes 0.01 mass% to 10.0 mass% Ge, 32.0 mass% to 40.0 mass% Sn, and the like. Further, it consists of the balance Au and inevitable impurities, and may further contain P, in which case the P content is 0.500% by mass or less.

  The Au—Ge—Sn solder alloy of the present invention is a main component in order to reduce the cost of Au—Ge solder and Au—Sn solder, which are very expensive, and to have excellent workability. Sn and Ge are added to Au. In other words, in a ternary alloy of Au, Sn, and Ge, based on the composition near the eutectic point, excellent workability and stress relaxation properties, and consequently high bonding reliability, and Sn and Ge Therefore, it is possible to reduce the Au content, so that it can be provided as a Pb-free solder material for high temperature use at a low cost.

  Hereinafter, elements essential to the Au—Ge—Sn solder alloy of the present invention and optional elements contained as necessary will be described in more detail.

<Au>
Au is a main component of the solder alloy of the present invention and is an essential element. Since Au is very difficult to oxidize, it is most suitable in terms of characteristics as a solder for joining and sealing semiconductor elements that require high reliability. Therefore, Au-based solder is frequently used for sealing quartz devices and SAW filters, and the solder alloy of the present invention is also based on Au, and provides a solder suitable for use in the above technical field.

  However, since Au is a very expensive metal, it is desirable not to use it from the viewpoint of cost. Therefore, it is rarely used for general-purpose products. On the other hand, the solder alloy of the present invention is mainly composed of Au, but is equivalent to Au-20 mass% Sn or Au-12.5 mass% Ge solder alloy in terms of characteristics such as bondability and reliability. In order to reduce the content and reduce the cost, Au and Sn are simultaneously contained in the Au as described later.

<Ge>
Ge is an essential element in the solder alloy of the present invention. Since Ge makes a eutectic alloy with Au and the solidus temperature can be lowered to 280 ° C., it has been practically used as Au-12.5 mass% Ge solder. However, since it contains nearly 90% by mass of Au, it is very expensive. In order to reduce the Au content, the solder alloy of the present invention has a composition in the vicinity of the eutectic point in the ternary Au—Ge—Sn alloy.

  In the Au—Ge—Sn ternary system, the composition of eutectic points is around Au = 47 atomic%, Ge = 6 atomic%, and Sn = 47 atomic%. That is, in mass%, Au = 60.6 mass%, Ge = 2.8 mass%, and Sn = 36.5 mass%. As can be seen from FIG. 1 showing the Au—Ge—Sn phase diagram, by setting the composition in the vicinity of the eutectic point, a solder alloy having excellent properties such as workability and stress relaxation properties can be obtained. In addition, since the melting point can be lowered to about 410 ° C., it becomes very easy to use as solder.

  The specific Ge content is 0.01 mass% or more and 10.0 mass% or less. If the Ge content is less than 0.01% by mass, the Ge content is too small, so that the effect of containing Ge does not substantially appear. On the other hand, if it exceeds 10.0% by mass, the liquidus temperature becomes too high, which makes it difficult to melt. Further, in the case where Sn is contained in the composition range of the present invention, if the content of Ge exceeds 10.0 mass%, the solder alloy is likely to be oxidized, and has high reliability that is characteristic of Au-based solder. Good bonding cannot be achieved.

  The particularly preferable Ge content is 2.0% by mass or more and 3.5% by mass or less, and if it is within this range, it is close to the composition of the eutectic point, has excellent workability, and has flexibility. Even better bonding is possible.

<Sn>
Sn is an essential element in the solder alloy of the present invention, and is an element indispensable for obtaining a composition near the ternary eutectic point.

  Au-12.5 mass% Ge solder and Au-20 mass% Sn solder, which are typical solders of Au-Ge alloy and Au-Sn alloy, have a composition of eutectic points, and thus the crystal is refined, It is relatively flexible. However, even if it is called a eutectic alloy, Ge is a semimetal, and in the case of Au-20 mass% Sn, since it is composed of an intermetallic compound, it is far more than general Pb solder or Sn solder. Hard and brittle.

  For this reason, it is difficult to process. For example, when processing into a sheet by rolling, the thickness can only be reduced little by little, so that productivity is poor, and a large number of cracks are likely to occur, and the yield tends to decrease. In the case of processing into a ball shape, for example, when the ball is formed by an atomizing method, the tip of the nozzle tends to be clogged, and the particle size distribution of the ball becomes wide, resulting in a low yield. In particular, in the case of atomizing in oil, the temperature during atomization cannot be raised to a temperature sufficiently higher than the solidus temperature (356 ° C.) of the Au—Ge alloy in order to prevent ignition and deterioration of the oil. In addition, the alloy is easily segregated, and the nozzle is easily clogged, resulting in a decrease in yield.

  By incorporating Sn into Au at the same time as Ge, it becomes possible to solve the problems of workability and productivity as well as problems such as reliability. That is, by containing Sn and Ge at the same time, it becomes possible to obtain a eutectic composition of Au-Sn intermetallic compound and Ge solid solution, the crystal becomes finer, workability, productivity, stress relaxation, and further reliability. It becomes a solder material with excellent properties. Naturally, by adding about 30 to 50% by mass of Sn and Ge in total, the cost can be greatly reduced as compared with typical Au-12.5% by mass and Au-20% by mass Sn.

  The specific Sn content is 32.0 mass% or more and 40.0 mass% or less. When the Sn content is less than 32.0% by mass, effects such as improvement in flexibility are not sufficiently exhibited, and the difference between the liquidus temperature and the solidus temperature becomes large, causing a phenomenon of separation. On the other hand, if the Sn content exceeds 40.0% by mass, the melting and separation phenomenon is likely to occur, and the Sn content that is likely to be oxidized as compared with Au is excessively increased, resulting in a decrease in wettability. There is a high possibility that it will end.

  The particularly preferable Sn content is 34.0% by mass or more and 39.0% by mass or less, and if it is within this range, the composition of the eutectic point is close and the above-described effect of Sn is sufficiently exhibited.

<P>
P is an arbitrary element that may be contained as necessary in the solder alloy of the present invention, and its effect is in improving wettability. The mechanism by which P improves the wettability is that the reducibility is strong, and by oxidizing itself, the surface of the solder alloy is suppressed and the substrate surface is reduced to improve the wettability.

  In general, even if Au solder is difficult to oxidize and is excellent in wettability, the oxide on the joint surface cannot be removed. However, P can remove not only the oxide film on the solder surface but also the oxide film on the bonding surface such as the substrate. Due to the effect of removing the oxide film on the solder surface and the joint surface, gaps (voids) formed by the oxide film can also be reduced. This effect of P further improves the bondability and reliability.

  Note that P does not remain on the solder, the substrate, or the like because the solder alloy or the substrate is reduced to become an oxide and is vaporized at the same time and flows into the atmosphere gas. 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 the solder alloy of the present invention contains P, the content of P is preferably 0.500% by mass or less. Since P is very reducible, the effect of improving the wettability can be obtained if a trace amount is contained, but the effect of improving the wettability does not change so much even if contained in excess of 0.5% by mass. Containment may cause a large amount of P or P oxide gas to increase the void ratio, or P may segregate by forming a fragile phase, embrittle the solder joint and reduce reliability. There is.

  Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to these examples.

  First, Au, Ge, Sn, and P each having a purity of 99.99% by mass or more were prepared as raw materials. Large flakes and bulk-shaped raw materials were cut and pulverized, etc. so as to be uniform, with no variation in composition depending on the sampling location in the alloy after melting, and were made fine to 3 mm or less. A predetermined amount of these raw materials was weighed and placed in a graphite crucible for a high-frequency melting furnace.

  In addition, when it contains P, when it melt | dissolves using a Sn-P alloy, since P which is easy to vaporize is alloyed from the beginning, since it becomes easy to make it contain in a solder, Sn-P alloy is used as a raw material. be able to.

  Next, the graphite crucible containing the raw material was placed in a high-frequency melting furnace, and nitrogen was flowed at a flow rate of 0.7 l / min or more per kg of the raw material 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 removed, and the molten metal in the crucible was poured into the solder mother alloy mold. A cylindrical mold having a diameter of 24 mm was used for submerged atomization.

  In this way, the solder mother alloy of Sample 1 was produced. Moreover, the solder mother alloys of Samples 2 to 22 were produced in the same manner as Sample 1 except that the mixing ratio of the raw materials was changed. About each solder mother alloy of these samples 1-22, the composition analysis was performed using the ICP emission-spectral-analyzer (SHIMAZU S-8100). The analysis results obtained are shown in Table 1 below.

  Each solder mother alloy of Samples 1 to 22 was processed into a ball shape using a submerged atomizer by the following method. As the liquid at that time, oil having a large effect of suppressing the oxidation of solder was used. The obtained balls of each sample were classified into a predetermined particle size by the following method, the yield was examined, and the workability was evaluated. The obtained ball yield (workability evaluation) is shown in Table 2 below.

<Ball manufacturing method>
Each solder mother alloy (diameter: 24 mm) of the prepared samples 1 to 22 is put into a nozzle of a submerged atomizer, and this nozzle is placed on the upper part of a quartz tube containing oil heated to 390 ° C. (in a high-frequency melting coil). I set it. The mother alloy in the nozzle was heated to 650 ° C. by high frequency and held for 5 minutes, and then the nozzle was pressurized with an inert gas and atomized to obtain a ball-shaped solder alloy. The ball diameter was set to 0.30 mm, and the nozzle tip diameter was adjusted in advance.

<Evaluation of workability (ball yield)>
In order to evaluate the workability of the solder alloy, the balls obtained by the above method using a biaxial classifier are classified within a range of diameter of 0.30 ± 0.015 mm, and the yield of the balls obtained by classification is determined. It was calculated by the following calculation formula 1.

[Calculation Formula 1]
Ball yield (%) = ball weight of diameter 0.30 ± 0.015 mm ÷ classified ball weight × 100

  Next, after performing the joining test with the substrate using each of the ball-shaped solder alloys of Samples 1 to 22 described above, the aspect of the joined solder is measured to evaluate the wettability, and the void ratio is measured. Therefore, the bondability was evaluated. Furthermore, the reliability evaluation by a heat cycle test was performed using the board | substrate and solder joined body obtained by the said joining test. The obtained aspect ratio (wetability evaluation), void ratio (bondability evaluation), and heat cycle test (reliability evaluation) results are shown in Table 2 below.

<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 flowed at a flow rate of 12 l / powder from four locations around the heater part . Thereafter, the heater was set to a temperature higher than the melting point by 50 ° C. and heated.

  After the heater temperature has stabilized at the set value, a Cu substrate (plate thickness: 0.3 mm) plated with Ni (film thickness: 3.0 μm) is set in the heater and heated for 25 seconds, and then a ball-shaped solder alloy Was placed on a Cu substrate and heated for 25 seconds. After the heating was completed, the Cu substrate was picked up from the heater part, once installed in a place where the nitrogen atmosphere next to it was maintained, cooled, and after sufficiently cooled, taken out into the atmosphere.

  The aspect ratio of the solder alloy 3 was determined for the obtained joined body, that is, the joined body in which the solder alloy 3 was joined to the Ni layer 2 of the Cu substrate 1 as shown in FIG. 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)>
For the joined body shown in FIG. 2 obtained in the same manner as in the evaluation of the wettability, the void ratio of the Cu substrate 1 to which the solder alloy 3 is joined is expressed by an X-ray transmission device (TOSMICRON-6125, manufactured by Toshiba Corporation). It measured using. Specifically, X-rays were transmitted vertically through the joint surface of the solder alloy 3 and the Cu substrate 1 from above, and the void ratio was calculated using the following calculation formula 3.

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

<Reliability evaluation (heat cycle test)>
The joined body shown in FIG. 2 obtained in the same manner as in the evaluation of the wettability was repeated a predetermined number of cycles, with -40 ° C. cooling and 250 ° C. heating taken as one cycle. Thereafter, a Cu substrate (bonded body) to which the solder alloy was bonded was embedded in the resin, cross-section polishing was performed, and the bonding surface was observed with SEM (S-4800, manufactured by Hitachi, Ltd.). The case where the joint surface was peeled off or the solder alloy was cracked was indicated as “X”, and the case where there was no such defect and the same joint surface as in the initial state was maintained as “◯”.

  As can be seen from Table 2, each of the solder alloys of Samples 1 to 11 according to the present invention exhibits good characteristics in each evaluation item. That is, the ball yield, which is an evaluation of workability, is high, and the yield is high even when compared with Au-12.5 mass% Ge of sample 21 and Au-20 mass% Sn of sample 22 which are comparative examples. I understand. 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 0.3%, indicating good bondability. And in the heat cycle test which is a test regarding reliability, no defect appeared even after 500 cycles, and good results were obtained.

  On the other hand, each solder alloy of Samples 12 to 22 as a comparative example had an undesirable result in at least any of the characteristics. That is, even if the ball yield was high, it was 46% which was lower than that of all the samples of the present invention, and the void ratio was 0.7 to 7.5%, which was clearly worse than that of all the samples of the present invention. Further, the aspect ratio was 4 or less except for samples 17, 21, and 22, and in the heat cycle test, defects occurred in all the samples up to 500 times except for samples 21 and 22.

  In addition, the solder alloys of the present invention of Samples 1 to 11 in the above examples have not only good results in the evaluation of the above characteristics, but the Au content is as low as 64.0% by mass at the maximum. This Au content is smaller than Au-12.5 mass% Ge of sample 21 and Au-20 mass% Sn of sample 22 which are the most common eutectic compositions in Au-Ge solder alloys. It can be seen that the Au—Ge—Sn solder alloy of the present invention is low cost.

1 Cu substrate 2 Ni layer 3 Solder alloy

Claims (5)

Ge contained 10.0 wt% 0.01 wt% and containing Sn or less 32.0 mass% or more 40.0% by weight, the balance Ri Do from Au and unavoidable impurities, the liquidus temperature and the solid An Au—Ge—Sn solder alloy for SAW filters or MEMS, characterized in that the difference from the phase line temperature is less than 50 ° C. The Ge is contained in an amount of 2.0 to 3.5% by mass, Sn is contained in an amount of 34.0 to 39.0% by mass, and the balance is made of Au and inevitable impurities. 2. Au—Ge—Sn solder alloy for SAW filter or MEMS according to 1. 3. The SAW filter according to claim 1, wherein, in addition to Ge, Sn, and Au, P is contained in an amount of 0.500% by mass or less with respect to a total of 100% by mass of Ge, Sn, and Au. Au-Ge-Sn solder alloy for use in MEMS or MEMS . A MEMS, which is sealed with the Au—Ge—Sn solder alloy according to claim 1.   A SAW filter sealed with the Au—Ge—Sn based solder alloy according to claim 1.

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