JP2016059943A - BALL-SHAPED Au-Ge-Sn-BASED SOLDER ALLOY AND ELECTRONIC COMPONENT USING THE SOLDER ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide at low cost, a Pb-free Au-Ge-Sn-based solder alloy for high temperature use excellent in wet spreadability and bondability, having high bond reliability and adequately usable for bonding and sealing electronic components such as a quartz crystal device or SAW filter for which extremely high reliability is required.SOLUTION: There is provided a ball-shaped Au-Ge-Sn-based solder alloy comprising 0.01-10.0 mass% Ge, 32.0-40.0 mass% Sn and the balance Au with inevitable impurities and having a ratio of major axis/minor axis of 1.00 to 1.20 or less. The major axis/minor axis ratio (X1/Z1), when mashing up the ball-shaped Au-Ge-Sn-based solder alloy from one direction, may be 1.00 to 1.50.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a high-temperature Pb-free solder alloy, and more specifically, a ball-shaped solder alloy containing Au, Ge, and Sn as main components, and an electronic component joined or sealed using the solder alloy About.

  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 also referred to as Pb-free solder, lead-free solder, or lead-free solder) has been actively conducted.

  Solder used for joining a semiconductor element to a substrate is roughly classified into high temperature (about 260 ° C. to 400 ° C.) and medium to low temperature (about 140 ° C. to 230 ° C.) depending on the limit temperature of use. With regard to the low-temperature solder, lead-free solder has been put into practical use with Sn as a main component.

  On the other hand, research and development has been conducted on various high-temperature Pb-free solders. For example, Patent Document 1 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 2 discloses a solder alloy in which a binary eutectic alloy is added to a eutectic 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. However, the required characteristics for use in electronic parts and the like have not been sufficiently satisfied, and have not yet been widely used.

  Pb-free solder materials for high temperatures include Au-20 mass% Sn alloy and Au-12.5 mass% Ge alloy, which are used in crystal devices, SAW filters, MEMS (microelectromechanical systems), etc. ing. With respect to other Au-based solder alloys, for example, in Patent Document 3, a plate-shaped low-melting-point Au alloy solder of Au—Ge, Au—Sb, or Au—Si is preheated and then provided with a heat insulating portion. It describes a pressing method for a plate-shaped low melting point Au alloy brazing, characterized in that the material is sequentially fed to a mold and pressed in a temperature range of 100 ° C. to 350 ° C.

  Patent Document 4 discloses a brazing material used for brazing of external leads 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 5 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.

  On the other hand, as the ball-shaped Pb-free solder, for example, Patent Document 6 describes a non-Au-based lead-free solder alloy such as a ball-shaped Sn—Ag—Cu alloy, and Patent Document 7 describes a sheet shape or a wire shape. Alternatively, a ball-like non-Au-based lead-free Zn-based solder alloy is described.

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 JP 2011-198777 A JP 2011-235342 A

  There are various reports and proposals regarding Pb-free solder materials for high temperatures other than the above-mentioned patent documents, but they are still lower in cost and versatility than Au-20 mass% Sn alloy and Au-12.5 mass% Ge alloy. No solder material has 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 1, since the liquidus temperature is as high as 400 to 700 ° C., the working temperature at the time of joining is estimated to be 400 to 700 ° C. or more, and the joining is performed. This will exceed the heat resistance temperature of the semiconductor element or substrate.

  In addition, Au-20 mass% Sn solder and Au-12.5 mass% Ge solder have been put to practical use as Au-based solders, but these Au-based solders use a large amount of very expensive Au, Compared to Pb solder, Sn solder, etc., it is very expensive. 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, many high-temperature Pb-free solder materials containing Au-based solder are very poor in ductility and are hard or brittle and difficult to process. For this reason, a ball-shaped solder alloy that requires almost no processing has been proposed, but a ball-shaped solder alloy that has sufficient surface oxidation prevention, good wetting and spreading, adhesion, and bondability has not yet been found. Absent.

  In order to cope with various problems of Au solder including the above problems, the techniques described in Patent Documents 3 to 5 have been proposed. However, the technique of Patent Document 3 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 processing has been carried out using a compound mold, but this compound mold technology also has a problem of mold accuracy and mold life, so a press mold with a heat insulation section is provided. Patent Document 3 discloses a technique in which materials are sequentially fed and pressed in a temperature range of 100 to 350 ° C. However, even in such warm press working, there are many problems as shown below.

  That is, in the warm press, the oxidation of the solder alloy proceeds. Therefore, even if it is a solder alloy containing a large amount of Au, Au-based solder containing other metals such as Ge, Sb, or Sn cannot prevent the progress of oxidation of these elements. When pressed at a high 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. In addition, the warm press has a problem that the equipment cost is higher than that of a normal press.

  Further, as described above, the above-mentioned Patent Document 4 contains 10 to 35 wt% of Ag, 3 to 15 wt% in total of at least one of In, Ge, and Ga, and the electromigration of an Au alloy composed of Au as the balance. 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 4 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, although the brazing strength after being left in a 1% NaCl solution has been evaluated, the bonding state including wetting and spreading has not been confirmed. In the reliability evaluation, it is necessary to carry out a temperature cycle test for confirming stress relaxation including the bonded state, etc., but the technique of Patent Document 4 is not carried out, and whether high reliability can be obtained. Is not confirmed.

  Further, the above-mentioned Patent Document 5 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− It describes a brazing material characterized in that Ts <50 degrees, which realizes Pb-free, does not melt to the reflow temperature, and the temperature for bonding is too high, for example, adhesive or It has been shown that a brazing material suitable for joining electrical and semiconductor elements that does not damage the component itself can be provided.

  However, the brazing material of the ternary alloy containing Au / Ge / Sn described in Patent Document 5 has a composition range that is too wide such that 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. When an Au-12.5 mass% Ge alloy (eutectic point composition) and an Au-20 mass% Sn alloy (eutectic point composition) are compared, the characteristics are clearly 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--to which a small amount of Sn is added. An Au-20 mass% Sn-Ge alloy to which a small amount of Sn alloy and Ge are added belongs to the composition range of Patent Document 5, but the characteristics of these two types of ternary alloy brazing materials 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 5 is less than 50 ° C. However, the melting point is still too low for high-temperature solder.

  Patent Document 6 and Patent Document 7 disclose ball-shaped lead-free solder alloys. Since these lead-free solder alloys are non-Au solder alloys, they can be easily processed and easily formed into a ball shape close to a true sphere. However, the solder alloy material must be melted at a high temperature in the process of the ball shape, but since the main component is composed of Sn and Zn, it is important and difficult to prevent surface oxidation. In some cases, the product may not be reliable.

  On the other hand, the Au-Ge-Sn solder alloy can easily prevent surface oxidation due to its composition compared to non-Au solder alloys, but it is inferior in workability and formability, so the ball does not become a true sphere. May be distorted. If distorted shapes are mixed, when soldering electronic components using ball-shaped solder, the conveyance in the soldering device will not be stable and the device will stop, or the ball-shaped solder will be placed in an appropriate position. Problems such as inability to install may occur.

  Even if the ball-shaped solder can be installed at an appropriate position, when ball-shaped solder having a distorted shape is mixed, the wetting and spreading property is not stable, and it is likely to cause a bonding failure. Furthermore, when melting ball-shaped solder with a laser, if mixed ball-shaped solder with a distorted shape is present, the amount of laser energy absorbed is difficult to stabilize, so the molten state tends to become unstable and worst case. In this case, solder may be scattered.

  The present invention has been made in view of the above-described conventional circumstances, has excellent wettability and bondability, and thus has high bonding reliability, and requires extremely high reliability such as a crystal device and a SAW filter. Can be sufficiently used for bonding and sealing, and is less expensive than conventional Au—Sn-based and Au—Ge-based high-temperature Pb-free solder alloys, and Pb-free ball-shaped Au for high-temperature applications. The object is to provide a -Ge-Sn solder alloy.

  In order to achieve the above object, the first ball-shaped Au—Ge—Sn based solder alloy provided by the present invention comprises 0.01% by mass or more and 10.0% by mass or less of Ge, and 32.0% by mass or more and 40% by mass or more. It is characterized by comprising 0.0 mass% or less of Sn, the balance of Au and inevitable impurities, and having a length-to-short ratio determined by a major axis / minor axis of 1.00 or more and 1.20 or less.

  In the first ball-shaped Au—Ge—Sn solder alloy according to the present invention, 2.0 mass% to 3.5 mass% Ge and 34.0 mass% to 39.0 mass% Sn are contained. And the remaining ratio of Au and inevitable impurities, and the length-to-length ratio determined by the major axis / minor axis is preferably 1.00 or more and 1.10 or less.

  Further, the second ball-shaped Au—Ge—Sn solder alloy provided by the present invention crushes the ball-shaped Au—Ge—Sn solder alloy after granulation from one direction, and a straight line portion in plan view is formed on the alloy surface. A ball-shaped Au—Ge—Sn based solder alloy having a shape of 0.01 to 10.0 mass% of Ge, 32.0 to 40.0 mass% of Sn, and Further, it is composed of the remaining Au and inevitable impurities, and the ratio of the length to the length obtained by the major axis / minor axis exceeds 1.00 and is 1.50 or less.

  In addition, the first or second ball-shaped Au—Ge—Sn solder alloy of the present invention described above can contain P in an amount of 0.50% by mass or less together with the above Au, Ge, and Sn.

  Furthermore, the present invention provides an electronic component characterized in that it is bonded or sealed using the first or second ball-shaped Au—Ge—Sn solder alloy.

  According to the present invention, high-temperature ball-shaped Au—Ge that does not contain lead and has various characteristics such as workability as compared with conventional Au-based solder, and in particular, is excellent in wet spreadability and bondability during bonding. A Sn-based solder alloy can be provided. Therefore, the ball-shaped Au—Ge—Sn solder alloy of the present invention is used not only for general bonding or sealing but also in places where extremely high reliability is required, such as crystal devices, SAW filters, and MEMS. can do.

  Furthermore, since the ball-shaped Au—Ge—Sn solder alloy of the present invention has a ball shape with an appropriate length-to-short ratio, it wets and spreads in a shape close to a perfect circle when melting at the time of bonding or sealing. High joint reliability can be obtained due to the wet spread. Therefore, the occurrence of defects is very small, and various yields in manufacturing are improved and improved. Therefore, various electronic components can be efficiently manufactured, and cost reduction can be realized. Therefore, it is possible to provide a ball-shaped Au-based solder excellent in various characteristics, and the industrial contribution is extremely high.

It is an Au-Sn-Ge system phase diagram. It is a perspective view which shows typically the ball-shaped solder alloy crushed from one direction. In a wettability test, it is a side view which shows typically the joined body by which the solder alloy was joined on Cu board | substrate which provided Ni layer. It is a top view which shows typically the measurement of the aspect ratio in a wettability test.

  The first and second ball-like Au—Ge—Sn solder alloys of the present invention are characterized by their composition in terms of Ge of 0.01 mass% to 10.0 mass% and 32.0 mass% to 40 mass%. It is composed of 0.0 mass% or less of Sn and the balance of Au and inevitable impurities. Further, as a feature of the shape, in the first ball-shaped Au—Ge—Sn solder alloy, the length-to-short ratio obtained by the major axis / minor axis is 1.00 or more and 1.20 or less, and the ball-shaped Au after granulation In the second ball-shaped Au—Ge—Sn solder alloy in which the Ge—Sn solder alloy is crushed from one direction and has a shape having a straight line portion in plan view, the above-mentioned ratio of length to length exceeds 1.00. .50 or less.

  In the present invention, the above first and second ball-shaped Au—Ge—Sn solder alloys reduce the cost of Au-based solder materials, which are very expensive, and have excellent workability. As a feature, Sn and Ge are added to Au as a main component. 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 high-temperature Pb-free solder material at a lower cost than conventional ones.

  Hereinafter, the characteristics in the composition of the first and second ball-like Au—Ge—Sn solder alloys of the present invention, that is, the essential elements and optional elements contained as necessary, and the contents thereof will be described in 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. 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, and simultaneously contains Au. In order to reduce the amount and reduce the cost, Sn and Ge are simultaneously contained in 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 the Au—Ge—Sn phase diagram shown in FIG. 1, a solder alloy having excellent properties such as workability and stress relaxation can be obtained by setting the composition in the vicinity of the eutectic point. In addition, since the melting point can be lowered to about 410 ° C., it can be very easily used 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. By alloying with three compositions of Au—Ge—Sn, eutectic points different from those of Au—Ge alloy and Au—Sn alloy are formed. It can be set as the composition of the eutectic point vicinity of the ternary system shown.

  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.

  Also, when processing into a ball shape, for example, when the ball is formed by the atomizing method, the tip of the nozzle tends to be clogged, and the discharge amount varies, so the particle size distribution of the ball becomes wide and the yield decreases. is there. Particularly in the case of atomization in oil, the temperature during atomization cannot be raised to a temperature close to the solidus temperature (356 ° C.) of the Au—Ge alloy in order to prevent ignition and deterioration of the oil. The alloy tends to segregate at the tip, and nozzle clogging is more likely to occur, leading to 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 Ge solid solution and Au—Sn intermetallic compound, 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 preferred Sn content is 34.0% by mass or more and 39.0% by mass or less, and within this range, it is close to the composition of the eutectic point, and the effect of Sn described above is more fully 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. The effect of P may further improve 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, if the addition amount is within the range of the present invention, it is unlikely that the residue of P will adversely affect reliability and the like. From this point, P can be said to be an excellent element.

  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. This is not preferable. Although P is effective even when added in a very small amount, it is preferably contained in an amount of 0.0001% by mass (1 ppm) or more.

  In addition, the ball-shaped Au—Ge—Sn solder alloy of the present invention has the first ball-shaped Au—Ge—Sn solder alloy as a feature in the shape so as to spread out in a state close to a perfect circle when melted. Then, the length-to-short ratio is set to 1.00 or more and 1.20 or less, and the ball-shaped Au—Ge—Sn based solder alloy after granulation is crushed from one direction so that the alloy surface has a linear portion in plan view. In the second ball-shaped Au—Ge—Sn based solder alloy, the length-to-short ratio needs to be more than 1.00 and not more than 1.50.

  Next, characteristics of the shapes of the first and second ball-like Au—Ge—Sn solder alloys of the present invention, that is, the length ratio of the solder alloys will be described.

<Long and short ratio>
In the present invention, the ball shape is not limited to a true spherical shape, but is used to include a football shape, an ellipse shape, and the like. In any of the above cases, the length ratio of the first ball-shaped Au—Ge—Sn solder alloy is as follows: the measured value at the longest diameter is the major axis, and the measured value at the shortest part is the minor axis. As shown in the calculation formula 1, the major axis is obtained by dividing the major axis by the minor axis, that is, the major axis / minor axis. The long diameter corresponds to the diameter of the smallest sphere circumscribing the ball-shaped solder alloy, and the short diameter corresponds to the diameter of the largest sphere inscribed in the ball-shaped solder alloy.

[Calculation Formula 1]
Long / short ratio = major axis ÷ minor axis

  Further, the second ball-shaped Au—Ge—Sn solder alloy, that is, the ball-shaped Au—Ge—Sn solder alloy after granulation is crushed from one direction to have a straight line portion in plan view on the alloy surface. In the case of the ball-shaped Au—Ge—Sn solder alloy having a shape, the diameter of the crushed ball-shaped solder alloy is the same as in the case of the first ball-shaped Au—Ge—Sn solder alloy. The length-to-short ratio is calculated in the same manner by the above-mentioned calculation formula 1, with the measured value at the longest part as the major axis and the measured value at the shortest part as the minor axis.

  In the case of the second ball-shaped Au—Ge—Sn based solder alloy, as shown in FIG. 2, the horizontal portion 2 on the horizontal substrate 2 with one of the straight portions 1a and 1b in plan view of the crushed ball-shaped solder alloy 1 facing down. In general, the minor axis corresponds to the thickness Z1 in the crushed direction (vertical direction), and the major axis corresponds to the diameter Z2 of the smallest circle circumscribing the figure projected on the horizontal substrate 2. In FIG. 2, in order to make it easy to distinguish the major axis from the minor axis, the ratio between the major axis and the minor axis obtained from Z1 and Z2 is exaggerated so as to be out of the scope of the present invention.

  In addition, the method of crushing the solder alloy from one direction is not particularly limited. For example, the solder alloy may be crushed by an appropriate width in the vertical direction using a warm press machine or the like. At this time, the method of crushing in the direction in which the short diameter of the ball-shaped solder alloy becomes shorter is a method that can be easily processed, but as a result, the method of crushing in the long diameter direction may be used if the length-to-short ratio falls within the above range.

  The ball-shaped Au—Ge—Sn solder alloy of the present invention has a length-to-short ratio defined as described above in the range of 1.00 to 1.20 in the first ball-shaped Au—Ge—Sn solder alloy. The second ball-shaped Au—Ge—Sn solder alloy is melted at the time of joining or sealing by being crushed from one direction so as to be in the range of more than 1.00 and not more than 1.50. Can spread out in a state close to.

  If the length ratio of the first and second ball-shaped solder alloys exceeds the upper limit of each of the above ranges, the solder does not spread circularly on the joint surface during melting, and locally or partially protrudes from the part to be joined or sealed. This may cause a short circuit with the adjacent conductive part, or a part that cannot be joined or sealed due to insufficient solder, resulting in a part that is not sufficiently alloyed. Further, if the amount of solder is partially increased, the thickness of the solder becomes non-uniform, which may cause chip tilt and the like.

  In order to eliminate the occurrence of such a problem, in the first ball-shaped Au—Ge—Sn based solder alloy of the present invention, the length-to-short ratio is set to a range of 1.00 to 1.20. If the length-to-short ratio is 1.20 or less, the solder spreads uniformly on the joint surface while approaching a circle due to surface tension during melting. However, if the length ratio exceeds 1.20, it becomes difficult to approach a circular shape due to the surface tension at the time of melting, and it becomes difficult to spread uniformly on the joint surface. Further, if the length ratio is 1.00 or more and 1.10 or less, the solder is more preferable because it becomes evenly circular on the joint surface while getting closer to a circular shape due to surface tension when melted.

  In the second ball-shaped Au—Ge—Sn solder alloy of the present invention, the length-to-short ratio is adjusted to be in the range of more than 1.00 and not more than 1.50. If the length-to-short ratio exceeds 1.50 during crushing, there is a risk that the Au—Ge—Sn solder alloy will crack, the crushed shape will be distorted, or in some cases, cracked. An Au—Ge—Sn solder alloy having cracks or a crushed shape cannot be spread in a circular shape when the solder is melted.

  When the second ball-shaped Au-Ge-Sn solder alloy of the present invention is used for bonding or sealing, the straight line portion of the crushed solder alloy in contact with the bonding surface or the sealing surface is in contact with it. Deploy. By arranging in this way, the solder alloy is installed on the joint surface or sealing surface in surface contact, so that it does not move after installation, such as rolling, and the installation position is not shifted, improving the positional accuracy. Can be achieved. By melting the solder alloy in this state, the solder alloy wets and spreads in a circular shape with high accuracy, and excellent jointability can be achieved.

  Further, as described above, by arranging the straight line portion in plan view so as to be in contact with the bonding surface or the sealing surface, the upper surface of the solder alloy also becomes a straight line portion in plan view. It is preferable because it is easier to hit uniformly than hitting the spherical surface, the laser light energy is transmitted uniformly and efficiently to the entire solder alloy, and melts more uniformly. Furthermore, even when the solder alloy is melted by heat transmitted from the joint surface or sealing surface, the contact portion with the joint surface or sealing surface to which heat is transmitted is a flat surface, so compared with the case where the contact portion is spherical. Thus, heat is transmitted uniformly, which is preferable.

  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 raw materials were cut and pulverized so as to be uniform and uniform in the alloy after melting without variation in composition depending on the sampling location. A predetermined amount of these raw materials was weighed and placed in a graphite crucible for a high-frequency melting furnace.

  Next, the graphite crucible containing the raw material was put into a high-frequency melting furnace, and nitrogen was allowed to flow into the graphite crucible at a flow rate of 0.7 liter / 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. As the mold, a cylindrical shape having a diameter of 24 mm was used for atomization in liquid.

  In the above method, each solder mother alloy of Samples 1 to 22 was produced from the combination of the mixing ratio of the raw materials, the length ratio of the obtained ball-shaped alloy, and the presence or absence of the ball-shaped alloy crushing step. Each solder mother alloy of Samples 1 to 22 was subjected to composition analysis using an ICP emission spectroscopic analyzer (SHIMAZU S-8100), and the obtained analysis results are shown in Table 1 below.

  Next, each solder mother alloy of the above samples 1 to 22 was granulated into a ball shape by using the submerged atomizing apparatus by the following manufacturing method. As the atomizing liquid in the liquid, oil having a great effect of suppressing the oxidation of the solder was used. Furthermore, about some samples, the ball after atomization was crushed and it was set as the shape which has a planar view linear part on the surface. For each of the obtained solder alloys of Samples 1 to 22, the major axis and minor axis were measured by the following method, the major / minor ratio was calculated from the major axis / minor axis, and the obtained results are shown in Table 1 below.

<Ball manufacturing method>
Each master alloy (diameter 24 mm) of the above samples 1 to 22 was put into a nozzle of a submerged atomizer, and this nozzle was set on the top of a quartz tube containing oil heated to 270 ° C. (in a high frequency melting coil). . After heating the mother alloy in the nozzle to 540 ° C. by high frequency and holding it for 5 minutes, 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. Each of the balls thus obtained was washed with ethanol three times and then dried in a vacuum dryer at 40 ° C. for 3 hours in a vacuum.

  About the samples 14-16 and 22 after drying, the ball | bowl was further crushed and it was set as the shape which has a planar view linear part on the surface. Specifically, using a warm press machine, while flowing nitrogen at a flow rate of 5 liters / minute to suppress oxidation, the ball was crushed with a mold heated to 200 ° C., held for 30 seconds, and then the nitrogen was removed. It moved to the filled side box, and it cooled and took out to normal temperature. The degree of crushing was adjusted so as to obtain a predetermined crushing amount by controlling the gap of the mold.

<Measurement of long diameter and short diameter and calculation method of long / short ratio>
About each ball-shaped solder alloy of sample 1-13 and sample 17-21, a diameter is measured about arbitrary 50 places with a three-dimensional measuring machine, and the shortest diameter and the maximum length are the longest diameter. It was.

  Moreover, about the samples 14-16 and 22 of the shape which crushed the ball | bowl, the width | variety (thickness) of the crushing direction was measured arbitrarily 10 places, the length with the smallest measured value was made into the short axis, and it crushed The distance between parallel lines circumscribing the shape of the ball as viewed from the direction perpendicular to the measurement direction of the short axis was arbitrarily measured at 10 points, and the longest measured value was taken as the long axis.

  By dividing the major axis by the minor axis from the major axis and the minor axis measured as described above, the major / minor ratio of each ball-shaped solder alloy of Samples 1 to 22 was calculated.

  Next, after performing a joining test with the substrate using each of the ball-shaped solder alloys of Samples 1 to 22 described above, the aspect ratio of the joined solder is measured by the following method to evaluate wettability. The void ratio was measured to evaluate the bondability. Furthermore, the reliability evaluation by a heat cycle test was performed using the joined body of the board | substrate and solder obtained by the said joining test. Table 2 below 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)>
Start up a wettability tester (device name: atmosphere control type wettability tester), cover the heater part to be heated with a double cover, and let nitrogen gas flow at a flow rate of 12 liters / minute from around the heater part. did. 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 obtained bonded body, that is, the bonded body in which the solder alloy 5 was bonded to the Ni layer 4 of the Cu substrate 3 as shown in FIG. Specifically, for the joined body 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 closer the aspect ratio is to 1.00, the closer the welded solder alloy 5 is to the perfect circle and the better the wettability.

[Calculation Formula 2]
Aspect ratio = X1 / X2

<Evaluation of bondability (measurement of void fraction)>
For the joined body shown in FIG. 3 obtained in the same manner as in the evaluation of the wettability, the void ratio of the Cu substrate 3 to which the solder alloy 5 is joined is determined using an X-ray transmission device (TOSMICRON-6125, manufactured by Toshiba Corporation). It measured using. Specifically, X-rays were transmitted vertically through the joint surface between the solder alloy 5 and the Cu substrate 3 from above, and the void ratio was calculated using the following formula 3.

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

  The solderability was evaluated based on the void ratio. That is, “◎” indicates that the void ratio is 0.0% or more and less than 1.0%, and “◯” indicates that the void ratio is 1.0% or more and less than 5.0%. A state where the void ratio was 5.0% or more and there was a problem in joining was indicated as “x”.

<Reliability evaluation (heat cycle test)>
The joined body shown in FIG. 3 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 above, each of the ball-shaped solder alloys of Samples 1 to 16 of the present invention exhibits good characteristics in each evaluation item. That is, it can be seen that the vertical and horizontal dimensions, which are evaluations of the wetting and spreading properties of the solder alloy, are all 1.02 or less and are spreading almost like a perfect circle, and the void ratio is 4% or less and a good bonding is achieved. Further, in the heat cycle test, which is an evaluation of reliability, no defect occurred up to 500 cycles in all the samples 1 to 16. Furthermore, when the composition of Ge and Sn was in a more preferable range, no defect was observed up to 700 cycles in the heat cycle test.

  The reason why good results were obtained in all the evaluation items in this way is that the ball-shaped solder alloy of the present invention has a shape in which the length-to-short ratio is appropriately controlled and has an appropriate composition. This is because it has excellent wettability and the like.

  On the other hand, each of the ball-shaped solder alloys of Samples 17 to 22 as the comparative example resulted in an undesirable result in at least any of the characteristics. Specifically, it can be seen that the aspect ratios are all 1.12 or more and the wet spreadability is very poor. Further, the void ratio is 7% or more in many samples, and in the heat cycle test, defects occurred in all samples up to 300 cycles. In addition, the ball-shaped solder alloy of the sample 22 that was too crushed with a length-to-short ratio of 1.65 generated cracks and became petals.

DESCRIPTION OF SYMBOLS 1 Ball-shaped solder alloy 1a, 1b Plane view linear part 2 Horizontal substrate 3 Cu substrate 4 Ni layer 5 Solder alloy

Claims (5)

  A ball-shaped Au—Ge—Sn based solder alloy comprising 0.01% to 10.0% by weight of Ge, 32.0% to 40.0% by weight of Sn, and the balance of Au And a ball-shaped Au—Ge—Sn based solder alloy having a length-to-length ratio of 1.00 to 1.20.   It is composed of 2.0 mass% or more and 3.5 mass% or less of Ge, 34.0 mass% or more of Sn and 39.0 mass% or less of Sn, and the balance of Au and inevitable impurities. 2. The ball-shaped Au—Ge—Sn solder alloy according to claim 1, wherein the ratio is 1.00 or more and 1.10 or less.   A ball-shaped Au—Ge—Sn based solder alloy obtained by crushing a ball-shaped Au—Ge—Sn based solder alloy after granulation from one direction into a shape having a linear portion in plan view on the alloy surface, 0.01 The length-to-length ratio obtained from the major axis / minor axis is 1 and consists of Ge of mass% to 10.0 mass%, Sn of 32.0 mass% to 40.0 mass%, the balance Au and inevitable impurities. A ball-shaped Au—Ge—Sn based solder alloy characterized by being over 0.000 and not more than 1.50.   The ball-shaped Au-Ge-Sn based solder alloy according to any one of claims 1 to 3, wherein P is contained in an amount of 0.500% by mass or less together with Au, Ge, and Sn.   An electronic component, which is bonded or sealed using the ball-shaped Au—Ge—Sn solder alloy according to claim 1.

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