JP2015106678A - Al RIBBON FOR BONDING AND MANUFACTURING METHOD THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al ribbon for bonding used for bonding an electronic component built in various devices using a semiconductor and a substrate, which is inexpensive and has high dimensional accuracy, in which oxide films or residual impurities are reduced, and with which stabilized bonding can be achieved, and to provide a manufacturing method therefor.SOLUTION: An Al alloy material principally composed of Al is rolled in the thickness direction and width direction by using a reduction roll set combining a thickness direction reduction roll and a width direction reduction roll in series, and then subjected to wire drawing by means of a variant dice immediately thereafter. An Al ribbon thus obtained contains 800 ppm or less of at least one kind of Ni, Si and P, in total, has an average crystal grain size of 2-250 μm, surface roughness Ra of 2.0 μm or less, and the thickness of the oxide film of 4.0 nm or less.

Description

  The present invention relates to an Al ribbon for bonding used for bonding an electronic component incorporated in various devices using a semiconductor and a substrate and a manufacturing method thereof.

  In various devices using a semiconductor, a wiring material such as Al or Cu is used to connect a connection electrode (bonding pad) provided on a semiconductor element and an external lead terminal (lead) provided on a semiconductor package. Ultrasonic wire bonding using a wire is generally performed. This connection method by wire bonding is a bonding method that breaks a very thin oxide film (for example, several nm) of a wire by pressurizing the connection portion of the wire or applying ultrasonic vibration energy, thereby enabling bonding of metals. Is the method.

  Under the circumstances where such wire bonding is widely performed, recently, with the rapid progress of semiconductor technology, a technology for bonding even a large capacity element by bonding is required. As a technique that meets such needs, for example, bonding using a ribbon-shaped wiring material has been proposed. That is, by changing the wiring material from a wire shape (circular cross section) to a ribbon shape (rectangular cross section), the cross-sectional area can be remarkably increased, and a large current can be flown. Can withstand well. As for the Al ribbon used for such bonding, the following techniques are disclosed.

  Patent Document 1 discloses a bonding ribbon that has an equivalent current capacity, is equal to or equal to or higher and can realize more stable bonding strength, and a bonding method using the bonding ribbon. A bonding ribbon provided on the surface and a bonding method using the same are disclosed. According to Patent Document 1, “the top portions of a plurality of convex portions that contact the surface to be joined are formed at the initial stage of bonding, and the positions and sizes thereof are set as desired. The spread of the new surface to be joined can be facilitated, and by reducing the area of the tops of the plurality of convex portions, friction between the ribbon and the adherend is easily generated and formed on the surface. It is possible to easily break the oxide film, and it is easy to generate the initial plastic flow, so a relatively small load and ultrasonic energy can ensure stable bonding strength compared to a ribbon with a flat bonding surface. Is described.

  Further, Patent Document 2 discloses the following characteristics of a bonding ribbon that can be uniformly bonded over the entire bonding surface every time even if bonded tens of thousands of times compared to the bonding ribbon, and can realize more stable bonding strength. A technique having In other words, the aluminum ribbon for ultrasonic bonding according to Patent Document 2 is an aluminum ribbon for ultrasonic bonding composed of an aluminum alloy having a purity of 99% by mass or more, in which the additive element and the balance are made of aluminum. It is an ultrathin tape structure that has been roll-rolled after wire drawing, the average value of the crystal grain size in the cross section of the ribbon is 5 to 200 micrometers (μm), and the surface roughness of the ultrathin tape has a surface roughness of Rz ≦ It is characterized by a mirror finish of 2 micrometers (μm).

  As described above, Al ribbons are being put into practical use and becoming widespread as partial substitutes for wires such as Al, which are wiring materials. However, since there are many problems as described below, this is the reason for Al ribbons as wiring materials. It is a hindrance to the ribbon market expansion.

  In other words, the semiconductor field is exposed to intense cost competition, and there is a strong demand for cost reduction from the market, and if the demand cannot be met, the technology itself cannot survive, and the same applies to Al ribbons. It is. In addition, since Al ribbons are used in general products such as in-vehicle use, the demand for cost reduction is particularly strong, and thus cost reduction is required for the expansion of the Al ribbon market.

  Also, a high level is required for the quality of the Al ribbon. For example, when the dimensional accuracy of the width and thickness of the Al ribbon is low, the allowable current of the Al ribbon also varies, which is not preferable. For example, when the thickness changes, the load and ultrasonic energy for obtaining sufficient bonding strength at the time of bonding change, and when the width changes, the bonding area also changes. Since it is practically impossible to change the joining conditions in accordance with such dimensional variations, an Al ribbon with high dimensional accuracy is required to obtain good joining properties and high joining reliability.

  Furthermore, with an Al ribbon, if the oxide film is thick at the time of bonding or if oil remains during ribbon cleaning, the bondability will be greatly reduced or the bonding strength will vary more than the wire. This phenomenon becomes a problem even in the case of a wire, but particularly in the case of an Al ribbon, since the bonding area per one is large and it appears remarkably, reduction of impurities such as an oxide film and oil is strongly demanded.

  As described above, the Al ribbon as a wiring material is required to be reduced in cost, high in dimensional accuracy, and reduced in oxide film and impurities. By solving these problems, the Al ribbon is further industrialized. It can be an important product. However, even with the technologies of the above-mentioned patent documents, an Al ribbon that sufficiently satisfies these requirements is not provided.

  For example, Patent Document 1 discloses a technique for realizing a stable bonding strength by providing a bonding ribbon with a plurality of convex portions on one surface on the bonding side. However, it is not easy to provide a plurality of convex portions on the bonding ribbon. That is, unlike the case where the convex portion is provided on the thick plate, the bonding Al ribbon used as the wiring material is generally very thin with a thickness of about 50 to 100 μm and hardly exceeds 200 μm. In order to form a convex part on such a thin Al ribbon, a considerably advanced technique is required, and therefore a considerable increase in cost is inevitable. This is because rolling is a general technique used in many fields, but the rolling technique of providing a plurality of convex portions on a thin metal foil of about 100 μm is not generally performed.

  Further, according to the above-mentioned Patent Document 1, since the convex portion is provided on the surface on the joining side to achieve a stable joining strength, the pressure force and energy at the time of joining are concentrated on the convex portion, and the oxide film or the like It is said that the strength per part area is improved. However, on the contrary, since the stress to be pressed becomes low in the concave portion, the joint strength of the concave portion is lowered, and it cannot be said that the strength of the whole joint portion is necessarily increased. Further, at locations where the deformation of the ribbon is remarkable due to partial stress concentration, it is conjectured that, on the contrary, the strength decreases or the cross-sectional area of the ribbon decreases, thereby reducing the bonding strength of the ribbon itself. In addition, since the protrusions are provided, stress concentration is more likely to occur when deformed into a loop shape during bonding as compared to those having no protrusions. As a result, depending on the position of the stress concentration and the magnitude of the stress, it may cause cracking, the loop will not bend properly, and sufficient bonding strength will not be obtained, or the bonding strength of the bonding surface will vary greatly It is thought that problems such as doing will occur.

  In the above-mentioned Patent Document 2, by making the additive element and the wire drawing condition within a specific range, even if tens of thousands of times are joined, it can be joined uniformly over the entire joint surface every time, and more stable joint strength is realized. In the manufacturing method of the bonding ribbon which can be performed, it is indispensable conditions for wire drawing to perform multistage wire drawing. However, when multi-stage drawing is performed, as the number of stages increases, work time and labor are required, and necessary jigs and the like increase. In addition, when trying to perform multi-stage drawing with one device, it is necessary to change the die, perform cleaning etc. for replacement, and adjust the tension of the wire according to its diameter each time. Inefficient. As a method for efficiently performing multi-stage wire drawing without such trouble, it is conceivable to prepare wire drawing devices corresponding to the multi-stage wire, and to change the diameter of the wire drawn by each device. By doing so, the wire drawing work can be greatly simplified, but it is obvious that the introduction of many apparatuses is costly, and it is necessary to widen the installation location of the equipment.

  Further, according to Patent Document 2, it is said that by adjusting the crystal grain size by adding Ni, Si, Mg, and Cu, variation in bonding strength is reduced and stable bonding strength can be obtained. However, even if the crystal grain size is adjusted, there is an oxide film which is the main cause of lowering the bonding property on the surface. It must be said that the improvement effect is small. For example, in the examples, there is a description that the aluminum ribbon material is heat-treated at 200 to 400 ° C. Although there is no detailed description on the heat treatment conditions, it is impossible to increase the Al oxide film having a strong reducing property even if the heat treatment is performed in an ultra-high vacuum furnace equipped with a turbo molecular pump, for example. In this case, it is considered that the oxide film of the Al ribbon is formed to a thickness of several tens to 10 nm, or a few tens of nanometers or more when viewed partially. If such a thick oxide film is formed, it is apparent that the effect of improving the bonding strength hardly appears no matter how the crystal grain sizes are uniform.

  Further, according to the above-mentioned Patent Document 2, since the circular cross section is deformed into a plate shape by roll rolling after multi-stage drawing, the amount of plastic deformation is greatly different in the width direction, and the residual stress is large. The strength is not good, cracks occur at the end, the yield decreases, the wire breaks, or the crystal grain size varies greatly in the width direction, causing variations in the bonding strength. End up. With such an Al ribbon, stable joining with sufficient strength is impossible, and the yield is poor, which is disadvantageous in terms of cost.

JP 2007-194270 A Japanese Patent No. 4212641

  As described above, there is a strong demand for cost reduction for the Al ribbon for bonding. In other words, the semiconductor field is exposed to intense cost competition, and price reductions of several percent per year are natural. A technology that cannot meet this cost reduction requirement cannot survive, and the same situation applies to Al ribbons. Furthermore, since the Al ribbon is used in general products such as in-vehicle use, there is a strong demand for cost reduction.

  In addition, Al ribbons are required to have high dimensional accuracy in terms of width and thickness. In other words, Al ribbons are frequently used in electronic parts that require high reliability such as in-vehicle use, and therefore high bonding reliability is required. There are many requirements necessary to obtain high joint reliability, but high dimensional accuracy is an essential and important requirement. For example, Al ribbons with low dimensional accuracy also vary in allowable current, so that electrical resistance increases and heat is generated at locations with a small cross-sectional area, which may damage surrounding members and lead to disconnection of the Al ribbon itself. Absent. Also, changing the thickness and width of the Al ribbon changes the optimum load and ultrasonic energy for obtaining sufficient bonding strength during bonding, but it is a reality to change the bonding conditions according to such dimensional variations. Is impossible. Therefore, in order to obtain good bondability and high bonding reliability, an Al ribbon with high dimensional accuracy is required.

  Furthermore, Al ribbons are required to reduce residual impurities such as oxide films on the surface and oil. That is, if the oxide film on the surface is thick, or if oil or impurities at the time of ribbon cleaning remain on the surface, the bondability at the time of bonding is greatly reduced or the bonding strength varies. This oxide film and residual impurities are also a problem with wires, but in the case of ribbons, since the bonding area per wiring material is large and the current flowing per wire tends to increase, the reduction is particularly important. .

  The present invention has been made in view of the problem of such an Al ribbon for bonding, and is inexpensive, has high dimensional accuracy, and has reduced surface oxide film, residual impurities, etc., so that stable bonding can be achieved. An object of the present invention is to provide an Al ribbon for bonding that can be realized and a method for manufacturing the same.

  In order to achieve the above object, a method for producing an Al ribbon for bonding provided by the present invention comprises a roll set for rolling in which a thickness direction rolling roll and a width direction rolling roll are incorporated in series, and an irregularly shaped die. A processing apparatus is used to roll an Al alloy material containing Al as a main component in a thickness direction and a width direction with a roll set for rolling, and thereafter, the Al alloy material is drawn with an irregularly shaped die.

  In addition, the Al ribbon for bonding provided by the present invention contains Al as a main component, contains at least one of Ni, Si and P in a total of 800 ppm or less, has an average crystal grain size of 2 to 250 μm, and has a surface roughness. The thickness Ra is 2.0 μm or less, and the thickness of the oxide film is 4.0 nm or less.

  According to the present invention, an Al ribbon for bonding with high dimensional accuracy such as width and thickness and reduced surface oxide film and residual impurities can be provided at low cost. Therefore, by using the bonding Al ribbon of the present invention, excellent bonding strength and high bonding reliability can be obtained, and stable bonding can be realized. Therefore, for electronic parts that require high reliability such as in-vehicle use. It is particularly useful.

It is the schematic which shows one specific example of the roll set for rolling, Comprising: (A) is a side view, (B) is a top view. It is a front view schematically showing a die hole of an irregularly shaped die, (A) is a rectangular die hole, (B) is a die hole in which a rectangular corner forms an arc, and (C) is a rectangular short side portion. A die hole forming an arc. It is the schematic which shows the Al ribbon bonded to the Ni plating Cu board | substrate in a joining strength test, (A) is sectional drawing and (B) is a top view.

  The Al ribbon of the present invention is manufactured by a rolling process using a rolling roll set in which a thickness direction rolling roll and a width direction rolling roll are incorporated, and a wire drawing process using an irregularly shaped die immediately after the rolling process. That is, the Al ribbon material of the present invention can be produced by simultaneously rolling the raw material Al alloy material in the thickness direction and the width direction using a rolling roll set, and then drawing with an irregularly shaped die immediately thereafter. it can.

Regarding the rolling by the above rolling roll set, a rolling roll set in which one set of thickness rolling direction roll A and width direction rolling roll B is incorporated in series with reference to FIG. 1 showing a specific example of the rolling roll set. with, a case is described in which rolling an Al alloy material 1 ₀ for rolling. Incidentally, FIG. 1 shows a case where Al alloy material 1 ₀ is cylindrical. Also, using multiple rolling roll sets may be repeated a plurality of times rolling in the thickness direction and width direction of the Al alloy material 1 _0.

First, the gap between the thickness direction rolling roll A and the width direction rolling roll B incorporated in series is adjusted according to the required dimension. Then, an Al alloy material 1 ₀ for rolling, scissors through the thickness direction rolling rolls A, passed through a widthwise rolling rolls B subsequently, the ends of the Al alloy material 1 ₀ through the widthwise rolling rolls B Set on a take-up spool attached to a take-up machine (not shown). Thereafter, the wound by rotating the winding machine automatic, Al alloy material 1 ₀ through the two rolling rolls in the thickness direction rolling rolls A and widthwise rolling rolls B, given in a single rolling operation Rolled to dimensions.

By rolling the Al alloy material 1 ₀ using a rolling roll set incorporating the above thickness rolling direction rolls A and widthwise rolling rolls B in series, the thickness and width directions with respect to Al alloy material 1 ₀ The two-direction rolling can be performed in one operation, so that high dimensional accuracy can be obtained and the production efficiency is very high, and it is possible to manufacture an Al ribbon with extremely low cost and high dimensional accuracy. it can.

  As described above, the Al alloy material rolled in one rolling operation in the thickness direction and the width direction by the rolling roll set is drawn by an irregularly shaped die immediately after that. Drawing with an irregularly shaped die is preferable because an Al ribbon can be efficiently produced by attaching an irregularly shaped die after the rolling roll set and continuously drawing immediately after the rolling operation. When the irregularly shaped die cannot be attached to the rolling device, it is possible to perform wire drawing using a wire drawing machine immediately after rolling.

  Further, the wire drawing by the irregularly shaped die may be performed in two or more stages. The dimensional accuracy can be further increased by drawing in multiple stages. As the material of the die, a super steel die or a diamond die can be used. Particularly, the diamond die is preferable because it is hard and has little wear and the like.

  The shape of the die hole of the irregularly shaped die, that is, the shape of the die hole in which the Al alloy material is drawn may be other than a circle, but is preferably a substantially rectangular shape as shown in FIG. For example, as shown in FIG. 2A, in addition to a die having a rectangular die hole (long side a ≠ short side b), as shown in FIG. 2B, four corners of the rectangle of the die hole shown in FIG. A die in which c forms an arc and a die in which short side portions d on both sides of the rectangle of the die hole in (a) form an arc as shown in (c) can be preferably used.

Hereinafter, the Al ribbon production method according to the present invention will be described in more detail.
<Al alloy material for rolling>
The Al alloy material for rolling used as a raw material is not particularly limited as long as it has Al as a main component, and may be one conventionally used as an Al ribbon. However, it is particularly preferable to use an Al alloy material containing 800 ppm or less in combination of at least one of Ni, Si and P, with the balance being Al and inevitable impurities.

  In addition, the shape of the Al alloy material for rolling is not particularly limited, and may be a plate shape, a foil shape, a columnar shape, or a wire shape as in the conventional case. For example, a wire-like Al alloy material may be manufactured by wire drawing, and the material of the die hole is preferably diamond rather than a super steel material. By using such a die, unevenness on the surface of the wire can be reduced, and scratches and the like are difficult to enter. When emphasizing quality, it is preferable to slow the wire drawing speed to such an extent that productivity does not drop so much. If the wire drawing speed is high, the surface of the Al alloy material becomes rough due to scratches, etc., so that meandering or the like is likely to occur during rolling or wire drawing, and the resulting Al ribbon has a different degree of plastic working in the length direction. This is not preferable because of the increased occurrence of

  In the case of an Al alloy material containing a large amount of additive elements, the material tends to be hard, and therefore it is preferable to use a taper die for the wire drawing die. By using a taper die, the wire drawing speed can be reduced, so that the stress applied to the Al alloy material does not become too high, and it becomes easy to obtain an Al wire of uniform quality in the wire drawing direction. This is because only the portion has a high stress, and it is easy to process even a hard material.

  The method for producing the Al alloy material used for producing the Al ribbon of the present invention is not particularly limited, and can be produced and prepared in the same manner as in the past. For example, Al and each additive element are melted at a high frequency in an inert gas, and then cast into a mold or an Al alloy is produced by a continuous casting machine. A high frequency melting type continuous casting furnace is preferable as a melting casting method because it can melt and cast a stable quality alloy in a large amount. The obtained Al alloy can be made into an Al alloy material having a predetermined shape such as a plate shape or a columnar shape as it is or after further drawing.

  Below, the manufacturing method of Al alloy material used for Al ribbon manufacture is concretely demonstrated to the case where the high frequency melt type continuous casting furnace is used as an example. First, Al having a purity of 99.995% by mass or more and additive elements having a high purity, for example, Ni, Si, and P having a purity of 99.95% by mass or more are prepared as raw materials. A predetermined amount of each raw material is weighed according to the target composition and put into a melting graphite crucible. A side hole is opened in the side surface near the bottom of the graphite crucible, and an aluminum alloy dummy material (aluminum alloy having a target composition) is packed therein to serve as a lid. When P is added, it tends to fly as a vapor at the time of dissolution, so it is better to add about 10 to 30% more than the target composition.

  Next, the graphite crucible containing the above raw materials is set in a high frequency melting type continuous casting furnace, and the continuous casting furnace is turned on while flowing an inert gas at a flow rate of about 0.5 to 2 liters / minute per kg of the raw material. The temperature is raised automatically by setting the temperature rise rate to 2 to 4 ° C./second. Then, it hold | maintains at about 80-200 degreeC higher than melting | fusing point by automatic operation, and after each raw material melt | dissolves, it stirs by inserting a stirring blade so that there may be no melt | dissolution residue and segregation. After confirming that the raw materials are sufficiently mixed, the molten raw material is slowly pulled out from the lateral hole near the bottom of the crucible at a constant speed to produce a rod-shaped Al alloy having a predetermined diameter (such as a circular or rectangular cross section). The obtained Al alloy is made into an Al alloy material as it is or by wire drawing as required.

<Rolling with a roll set for rolling>
Rolling by a rolling roll set in the present invention is a method in which the Al alloy material is rolled simultaneously in the thickness direction and the width direction by a single rolling operation. As shown in FIG. 1, the roll set for rolling to be used has a structure in which the thickness direction rolling roll A and the width direction rolling roll B are set in one set, and the thickness direction rolling roll A and the width direction rolling roll B are incorporated in series. It has. Rolling rolls set of thickness direction rolling rolls A and widthwise rolling rolls B may be at least one set, but the rolling rolls set with multiple sets installed in the thickness direction and width direction of the Al alloy material 1 ₀ rolling Processing can be repeated multiple times.

Moreover, you may arrange | position either the thickness direction rolling roll A and the width direction rolling roll B in the entrance side of rolling. Often between thickness direction rolling rolls A and widthwise rolling rolls B are provided with a guide, Al alloy material 1 ₀ may be a guide to roll doorway upon departing enter or roll. Furthermore, each roll of the thickness direction rolling roll A and the width direction rolling roll B may be driven by power, or may be a simple roll that does not use power. The gap between the rolls may not be adjustable, but may be adjustable and may be appropriately used depending on the size, accuracy, workability, and the like.

  By simultaneously rolling in two directions using the above-mentioned roll set for rolling, it is possible to roll with high dimensional accuracy, particularly with high dimensional accuracy in the width direction, compared to the case of rolling only in the thickness direction or width direction. it can. That is, since the width direction cannot be adjusted in general rolling, the width direction dimension greatly varies. In particular, when a wire-like Al alloy material is rolled into an Al ribbon, not only the dimensional accuracy in the width direction is very bad, but also the rolling ratio is different at the center and the end in the width direction of the Al ribbon. Cracks are likely to occur. Moreover, if it is going to suppress generation | occurrence | production of a crack, the frequency | count of rolling will increase very much and efficient production cannot be performed. In the present invention, by performing the two-way rolling in one operation, the above-mentioned general rolling problems can be solved, high dimensional accuracy can be obtained, and the production efficiency can be greatly increased. In addition, a low-cost Al ribbon can be manufactured.

  In addition, when rolling a metal material, it is common that metal powder (slag) generate | occur | produces, and the metal powder generated by the rolling process tends to adhere to a rolling roll. Thus, when a rolling roll with metal powder adhered to the surface or a rolling roll with a large surface roughness, that is, with many irregularities on the surface and a large difference in height, the rolled Al ribbon has dents or cloudiness on the surface. There is a problem that involves. Al ribbons with dents or the like on the surface may have different bonding strength, or the cross-sectional area may be reduced and the allowable current may be locally reduced. Therefore, in order to produce an Al ribbon with as few dents as possible, it is important to use a roll with a small surface roughness and to work while wiping off the lubricating oil supplied during rolling.

<Wire drawing with irregularly shaped dies>
In the present invention, as described above, the thickness direction and the width direction are rolled by a single rolling operation by the rolling roll set, and the wire is drawn by an irregularly shaped die immediately thereafter. That is, an Al ribbon can be efficiently manufactured by attaching a deformed die as shown in FIG. 2 after the rolling roll set and performing a wire drawing operation immediately after the rolling operation. However, when the irregularly shaped die cannot be attached after the rolling roll set, the wire drawing may be performed using a wire drawing machine immediately after the rolling operation.

  The Al alloy material can be made into an Al ribbon having a flat cross-sectional shape such as a rectangular shape by drawing using an irregularly shaped die whose shape of the die hole is other than circular, and the dimensions are higher than in the case of only rolling. An Al ribbon can be manufactured with high accuracy. And manufacturing cost can also be reduced significantly by performing rolling and wire drawing simultaneously by one operation | work.

  In the above rolling and wire drawing, processing is performed with lubricity while supplying lubricating oil so that scratches and the like generated on the Al ribbon are reduced and the surface is clean. As lubricating oil, mineral oil, vegetable oil, etc. can be used, and what mixed mineral oil and vegetable oil in the ratio of 1: 2.5 by weight ratio may be used.

  Further, before, during or during the rolling and wire drawing, or when the Al alloy material or the Al ribbon is hard or lacks flexibility, a heat treatment (annealing) may be performed as necessary. Hot rolling may be performed. The purpose of the heat treatment is to adjust strength, elongation, flexibility, workability, etc. by controlling the metal structure, and the temperature is preferably about 50 to 400 ° C., and the effect becomes great when it is 120 to 380 ° C. Therefore, it is more preferable. However, when performing heat treatment, it is necessary to pay sufficient attention to the heat treatment temperature, oxygen concentration, and the like. The reason is that if the heat treatment temperature is raised too much or the oxygen concentration is too high, the oxide film on the surface of the Al ribbon becomes thicker than 4.0 nm, and depending on the conditions, the thickness becomes several hundreds of nm or more and bonding becomes impossible. It is.

  After the rolling and wire drawing, in order to remove the lubricating oil from the surface of the obtained Al ribbon, it is washed with an organic solvent by an automatic washing machine or the like. As the organic solvent to be used, an organic solvent that can easily dissolve the lubricating oil and that does not easily remain in the ribbon material is preferable. Specific examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl ethyl ketone, acetone, methylene chloride, benzene, and toluene. In particular, methyl alcohol dissolves lubricating oil well and has high volatility. A solvent is preferable because it hardly remains in the ribbon material.

  As described above, after the lubricating oil is washed and removed from the Al ribbon, the Al ribbon may be slit if necessary. When slitting, a soft Al ribbon tends to generate burrs, so it is necessary to use a slitter that can be cut well and is well-maintained.

Next, the Al ribbon of the present invention will be described in detail.
<Composition of Al ribbon>
The Al ribbon of the present invention contains at least one of Ni, Si and P in an amount of 800 ppm or less, preferably an Ni content of 1 ppm or more and 150 ppm or less, with the remainder inevitably contained. Except for Al.

  First, Al, which is the main component of the Al ribbon of the present invention, is an excellent electrical conductor and is a very light element, and is therefore very excellent as a wiring material. For this reason, Al has been conventionally used as a wiring material. However, since Al alone is inferior in bonding property, bonding property, weather resistance, and the like, at least one of the following Ni, Si, and P is contained in order to obtain a highly practical wiring material.

  Ni and Si have effects similar to each other, and the greatest effect is in the reducibility inferior to that of Al. In other words, since Ni and Si are less likely to be oxidized than Al, if included in the Al ribbon, the Al ribbon itself is less likely to be oxidized and helps prevent oxidation. Furthermore, since Ni and Si are less reactive with acids and the like than Al, they contribute to improving corrosion resistance. As described above, since the oxide film at the joint is a major cause of deterioration of the bondability, the effect of containing Ni and Si is great. In fact, during bonding, heat is generated and oxidation easily proceeds, so the additive elements Ni and Si are more effective in preventing oxidation, and the corrosion resistance after bonding is improved, resulting in high reliability. It becomes possible to have a joint.

  The second effect of Ni and Si is in the control of the crystal structure of the Al ribbon. By containing appropriate amounts of these elements, the crystal grain size and shape can be controlled, and an Al ribbon with less variation in strength and elongation can be produced. The characteristic requirements for the Al ribbon vary from user to user and must be tailored individually. For example, if the Al ribbon is too hard, the repulsive force when bent in a loop shape during bonding is strong, and in particular, if the oxide film on the bonding surface varies, uniform bonding cannot be achieved, and in some cases, bonding cannot be performed. On the other hand, when the soft material is focused only on the loop property, there is a high possibility that burrs will be generated on the ribbon cutting surface, or a problem that a large amount of cutting waste will be generated and foreign matter will be mixed. Therefore, in order to meet the needs of each user, it is necessary to adjust the bonding strength, elongation, and further, loops and variations thereof. For this reason, at least one of Ni and Si is contained, the crystal grain size, etc. It is effective to control.

  Moreover, the Al ribbon of the present invention can contain P. In general, the surface of metal is covered with an oxide film except in special cases. A metal that easily oxidizes, such as Al, is naturally covered with an oxide film, and when hot-rolled or heat-treated, an oxide film of several tens nm or more may be formed depending on conditions. . On the other hand, the external lead terminal of the substrate is Cu or the joint surface thereof is Ni-plated, but there is no difference in having an oxide film as well. It is not easy to break down the oxide film or the residual oil due to insufficient cleaning, and obtain a stable bonding strength.

  P plays a major role in solving this problem. Since the Al ribbon containing P reduces the bonding surface due to the strong reducibility of P during bonding, it can be bonded without impurities such as oxygen, and the bonding strength can be significantly improved. After reducing the bonding surface, P itself becomes a gaseous oxide and scatters. Therefore, P remains on the bonding surface and does not cause a problem. In this respect, P can be said to be a very excellent element. It is presumed that the above-described effect of P is also present against impurities such as residual oil. Although it depends on the component of impurities, oxides that cannot be reduced by P are rare, and most elements can be reduced. Further, when P is vaporized after reduction, there is an effect that impurities are scattered together. Due to the above effects, the Al ribbon containing P can exhibit very excellent performance.

<Average crystal grain size, surface roughness, oxide film>
The Al ribbon of the present invention has an average crystal grain size of 2 to 250 μm, an average surface roughness Ra of 2.0 μm or less, and an oxide film thickness of 4.0 nm or less.

  The reason why the average crystal grain size of the Al ribbon is set to 2 μm to 250 μm is to set the strength, the elongation rate, and the like to appropriate values. That is, by adding Ni and Si as described above and controlling the grain size and shape of the crystal, it is possible to produce an Al ribbon having appropriate values for strength and elongation and less variation. Since the characteristic requirements for the Al ribbon vary depending on the user and must be adjusted individually, it is necessary and important to control the grain size and shape of the crystal.

  For example, if the Al ribbon is too hard, the repulsive force when bending into a loop shape during bonding will be strong, especially if there is variation in the oxide film on the bonding surface, uniform bonding will be difficult, and in some cases it will not be possible to bond To do. On the other hand, when the soft material is focused on only the loop property, there is a high possibility that burrs will be generated on the ribbon cut surface, or that a large amount of cutting residue will be generated and foreign matter will be mixed. In order to prevent such problems from occurring, it is necessary to adjust the bonding strength, elongation, loops, and variations of these in order to respond to each user's needs. For this reason, it is important to control the crystal grain size and shape. It is.

  Moreover, the reason why the average surface roughness Ra of the Al ribbon is set to 2.0 μm or less is that when the average surface roughness Ra exceeds 2.0 μm, the area which is substantially bonded becomes small at the time of bonding. This is because the bonding strength is lowered or the variation thereof is increased. If the average surface roughness Ra is 2.0 μm or less, it is possible to stably bond with high bonding strength. If the average surface roughness Ra is 1.0 μm or less, even better bonding is possible.

  The reason why the thickness of the oxide film is 4.0 nm or less is that when there is something other than the metal bonded between the bonding surface of the substrate and the Al ribbon, the metals cannot directly contact each other, and the bonding strength This is because of the decrease. In order to break the oxide film, bonding is performed by vibration energy of ultrasonic waves. However, if the thickness of the oxide film exceeds 4.0 nm, good bonding cannot be performed. If the thickness of the oxide film is 3.0 nm or less, it is more preferable because better bonding is possible.

  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, Al having a purity of 99.995% by mass or more and Ni, Si, and P having a purity of 99.95% by mass or more were prepared as raw materials, and melt cast by the following procedure using a high-frequency melting type continuous casting furnace. That is, a predetermined amount of each raw material was weighed according to the target composition and put into a melting graphite crucible. The graphite crucible containing the raw material was set in a high frequency melting type continuous casting furnace, and nitrogen gas was allowed to flow at a flow rate of about 0.8 liter / min per kg of the raw material. With the nitrogen gas flowing, the continuous casting furnace was turned on, and the temperature was raised automatically by setting the heating rate to 3 ° C./second.

  Thereafter, the temperature was maintained at about 850 ° C. by automatic operation, and after each raw material was melted, a stirring blade was inserted and stirred so that there was no undissolved residue or segregation of each element. After confirming that the raw materials were sufficiently mixed, the molten raw material was slowly pulled out from the lateral hole near the bottom of the crucible at a constant speed with stirring, to obtain a rod-shaped Al alloy having a diameter of 4.0 mm.

  By repeating the above operation except changing the input amount of each raw material into the graphite crucible, the Al alloys of Samples 1 to 25 which are examples of the present invention and the Al alloys of Samples 26 to 43 which are comparative examples. An alloy was prepared. The composition of each Al alloy of Samples 1 to 43 was analyzed using an ICP emission spectroscopic analyzer (SHIMAZU S-8100). The obtained analysis results are shown in Table 1 below for the Al alloys of Samples 1 to 25 and in Table 2 below for each of the Al alloys of Samples 26 to 43.

  Each Al alloy (diameter: 4.0 mm × length: 20 m) of Samples 1 to 43 shown in Table 1 and Table 2 above is used with two taper dies having a diameter of 2.0 mm and a diameter of 0.8 mm by a wire drawing machine. By drawing in two stages, the wire was drawn into a wire shape having a diameter of 0.80 mm to obtain an Al alloy material for rolling. That is, a lubricating oil in which mineral oil and vegetable oil were mixed at a weight ratio of 1: 2.5 (volume ratio) was prepared, and the Al alloy of each sample to which this lubricating oil was applied was set in a wire drawing machine. After being fixed to the take-up roll through the wire, the wire was drawn while being pulled at a constant speed by automatic operation. During drawing, the wire was drawn while supplying an appropriate amount of lubricating oil so that a wire-like Al alloy would not get caught or scratched.

  Each of the obtained Al alloy materials (diameter 0.80 mm) for rolling of Samples 1 to 43 is a rolling roll set in which a thickness direction rolling roll and a width direction rolling roll are incorporated in series, or a normal rolling roll. Was rolled using. Immediately thereafter, an Al ribbon was manufactured by drawing using an irregularly shaped die or slitting using a normal slitter. Note that all the samples were subjected to the above-described lubricating oil so as not to cause scratches or the like during rolling and wire drawing, and the rolling was cold rolling so that oxidation did not proceed.

  More specifically, at the time of the rolling process, Samples 1 to 21, 25, and 29 are one set of rolling roll sets, Sample 22 is the same two sets, Sample 23 is the same three sets, and Samples 24 and 30 are the same. Four sets were used for rolling. The target dimensions were a thickness of 0.100 mm and a width of 0.500 mm. In the case of rolling with a multi-stage roll set, rolling was performed gradually. On the other hand, for Samples 26 to 28 and Samples 31 to 43, a rolling roll set was not used, and rolling was performed with a target value of 0.100 mm only in the thickness direction using one normal rolling roll.

  Moreover, in the case of the said wire-drawing process, the sample 1-30 attaches the unusually shaped die (die hole shown to FIG. 2 (b)) to the rolling mill beforehand, and a target dimension is thickness with the unusually shaped die. The wire was drawn into a shape of 0.100 mm and a width of 0.500 mm. On the other hand, Samples 31 to 43 were slit using a slitter with a target width of 0.500 mm without using an irregularly shaped die.

  About each Al ribbon of the samples 1-43 manufactured by the above rolling process and wire drawing process, annealing with an electric furnace and polishing with abrasive paper are performed according to each sample, thereby obtaining an average crystal grain size and surface roughness. Ra and the thickness of the oxide film were adjusted. For example, the average crystal grain size was controlled by heat treatment in an electric furnace. In particular, Samples 4 to 6, 31 to 33 were heat-treated so as to obtain a target average particle diameter with care. Specifically, the Al ribbon of each sample was put in a hermetic batch electric furnace capable of evacuation and annealed at a temperature of 120 to 350 ° C. The annealing time was 30 minutes after reaching the target temperature.

  The surface roughness Ra was adjusted by polishing with abrasive paper. In particular, samples 7 to 9 and 34 to 36 were polished with care so as to achieve the target average surface roughness. Specifically, polishing papers of # 220 to # 5000 were prepared and polished according to the target average surface roughness. The thickness of the oxide film was adjusted by the atmosphere during the heat treatment after removing the oxide film as much as possible from the surface of the Al ribbon of each sample by acid treatment. In particular, for Samples 10 to 12 and 37 to 39, the ratio of the mixed gas was adjusted so that the oxide film has a target film thickness with care. Specifically, when the heat treatment is performed, the sample is placed in an electric furnace and then evacuated, and then pure nitrogen gas and pure oxygen gas are mixed according to the target oxide film thickness, Heat treatment was performed while flowing a mixed gas.

  About each Al ribbon of the obtained samples 1-43, while measuring an average crystal grain diameter, surface roughness Ra, and the thickness of an oxide film, the width | variety and thickness dimension variation, an external appearance inspection (inspection of a crack, a burr | flash, etc.) The bonding strength after bonding and the elongation rate were evaluated. Below, each measurement method of average crystal grain size, surface roughness Ra, thickness of oxide film, dimensional variation of width and thickness of Al ribbon, appearance inspection, bonding strength after bonding, measurement and evaluation of elongation rate Will be described in detail.

<Measurement of average crystal grain size>
After etching the sample Al ribbon using 2% nitric acid and 5% hydrofluoric acid, 20 crystal grain sizes were arbitrarily measured using a microscope (manufactured by Keyence Corporation, model: VHX-900). The crystal grains are not necessarily spherical, and most of them have a polygonal shape or a complicated shape, but the average value of the longest diameter and the shortest diameter is obtained and used as the average crystal grain diameter of the sample.

<Measurement of surface roughness Ra>
The average surface roughness Ra was measured using a surface roughness measuring device (manufactured by Tokyo Seimitsu Co., Ltd., model: Surfcom 470A). The surface roughness Ra was measured at three points in each of the rolling direction and the direction perpendicular to the rolling direction of the Al ribbon of the sample, and the average value of a total of 6 points was obtained to obtain the surface roughness Ra of the sample.

<Measurement of oxide film thickness>
The thickness of the oxide film was measured using a field emission Auger electron spectrometer (manufactured by ULVAC-PHI, model: SAM-4300). With respect to the Al ribbon of the sample, the thickness of the oxide film was measured at three arbitrary points, and the average value of the three points was obtained as the thickness of the oxide film of the sample.

<Measurement of dimensional variation>
With respect to the Al ribbon of the sample, the thickness and width were arbitrarily measured with an optical microscope at five points, and the average value of each was obtained. The difference (absolute value) between the average value of the obtained thickness and width and the target value of thickness and width (target value of thickness = 0.100 mm, target value of width = 0.500 mm) is the dimension of the sample. It was uneven.

<Appearance inspection (inspection for cracks and burrs)>
The appearance of the Al ribbon of the sample was inspected for cracks and burrs. The appearance inspection was first performed without using anything, and when it was difficult to visually determine, the appearance was inspected using an optical microscope (VHX-900 manufactured by Keyence Corporation). The case where there were no cracks or burrs per 10 m length of the Al ribbon was evaluated as ◯, the case of 1 to 3 was evaluated as Δ, and the case of 4 or more was evaluated as ×.

<Joint strength test>
The sample Al ribbon was bonded in order to confirm the bonding strength, and then a shear test of the bonded portion was performed. That is, as shown in FIG. 3, the Al ribbon 1 was pressed against the Cu substrate 3 on which the Ni plating 4 was applied, and the connection was made by applying ultrasonic vibration for 85 ms. Note that a sample in which an Al ribbon was bonded to a semiconductor element could not be set in a shear tester and could not be evaluated with high accuracy, so a Ni plated Cu substrate was used. The measurement sample (Cu substrate 3 to which the Al ribbon 1 is connected) thus prepared is fixed to a shear tester, and the bonding strength when the bonding portion 2 is peeled off by hooking the tip of the Al ribbon 1 with a jig. It was measured. The bonding strength was shown by the relative evaluation of each sample with Sample 1 as 100%.

<Elongation>
For the sample Al ribbon, the elongation was measured as an index of loop property and softness. That is, the Al ribbon was cut into a length of 100 mm, and the elongation was measured using a tensile tester (A & D Corporation, model: RTG-1240). Five points of each sample were prepared and the elongation rate was measured, and the average of a total of 5 points was obtained to obtain the elongation rate. Elongation was shown by relative evaluation of each sample with sample 1 as 100%.

  For each of the Al ribbons of Samples 1 to 43, the average crystal grain size, surface roughness Ra, and thickness of the oxide film obtained by the above method are shown in the following table together with the rolling means and wire drawing means used for the production thereof. Shown in 3-4. The evaluation results of dimensional variation, appearance inspection, bonding strength and elongation obtained by the above method are shown in Tables 5 to 6 below together with the working time of each sample evaluated relative to Sample 1 as 100%. The Al alloys of Samples 1 to 25 are shown in Tables 3 and 5 below, and the Al alloys of Samples 26 to 43 are shown in Tables 4 and 6 below.

  As can be seen from Tables 3 and 5, the Al ribbons of Samples 1 to 25, which are examples of the present invention, show good results in all evaluation items. Specifically, in all of the samples 1 to 25, the dimensional variation is small, the working time is short compared to each sample of the comparative example, no cracks or burrs are confirmed in the appearance inspection, and the bonding strength and elongation are all compared. High values were obtained compared to the examples.

  As described above, the reason why the dimensional variation was small for the Al ribbons of Samples 1 to 25 was that the thickness direction and the width direction were simultaneously rolled at the time of rolling, and the wire was drawn with an irregularly shaped die immediately thereafter. It is thought that it was obtained. By rolling in the thickness direction and width direction at the same time and performing rolling and wire drawing at the same time in this way, positional deviation and distortion are eliminated, and the occurrence of meandering, warping, wrinkles, etc. is reduced, and high-precision processing is achieved. Can do. In the samples 1 to 25 of the above examples, there was no meandering during the rolling, no warping or wrinkles were generated, and the rolling operation was easily performed and efficient production was possible.

  Moreover, the reason why the working time was short for the Al ribbons of Samples 1 to 25 was that the biggest factor was that the rolling and wire drawing in one operation were possible. The reason why cracks and burrs did not occur is that the maximum stress can be reduced by rolling from two directions, and it is not too soft and not brittle, and it is considered that a material having appropriate hardness and ductility is selected. . The reason why the bonding strength and elongation rate are high is considered that the average crystal grain size, the average roughness Ra, and the thickness of the oxide film satisfy the requirements of the present invention in addition to the absence of cracks and burrs as described above. .

  On the other hand, as can be seen from Tables 4 and 6, the Al ribbons of Samples 26 to 43, which are comparative examples, showed undesirable results in at least one of the characteristics. Specifically, for the samples 26 to 28 and the samples 31 to 43, the working time exceeds 180%, which is a factor that increases the cost. Samples 31 to 43 had extremely bad evaluation results with a bonding strength and elongation of 60% or less. Further, in Samples 29 to 30, the dimensional variation was slightly large, and some cracks and burrs were recognized in the appearance inspection.

A Thickness direction rolling roll A
B widthwise rolling rolls 1 ₀ Al alloy material 1 Al ribbon 2 junction 3 Cu substrate 4 Ni plating

Claims (5)

  Using a rolling roll set in which a thickness direction rolling roll and a width direction rolling roll are incorporated in series, and a processing device constituted by a deformed die, a roll set for rolling an Al alloy material mainly composed of Al A method for producing an Al ribbon for bonding, comprising: rolling in the thickness direction and width direction, and drawing with an irregularly shaped die immediately thereafter.   The method for producing an Al ribbon for bonding according to claim 1, wherein a plurality of sets of rolling rolls are used and rolling in the thickness direction and width direction of the Al alloy material is repeated a plurality of times.   3. The bonding Al according to claim 1, wherein a die having a rectangular die shape or a rectangular corner or short side forming an arc is used as the irregularly shaped die. Ribbon manufacturing method.   It contains Al as a main component, contains at least one of Ni, Si and P in a total of 800 ppm or less, has an average crystal grain size of 2 to 250 μm, has a surface roughness Ra of 2.0 μm or less, and is oxidized. An Al ribbon for bonding, wherein the thickness of the film is 4.0 nm or less.   The Al ribbon for bonding according to claim 4, wherein the Ni content is 1 ppm or more and 150 ppm or less.

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