JP2014096403A - Bonding wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding wire good in bondability with an Ni/Pd/Au covered electrode (a) or an Au covered electrode (a), excellent in thermal shock resistance, and having an inexpensive price as compared with a gold bonding wire.SOLUTION: A bonding wire W for performing connection by means of a ball bonding method contains 1.0 mass% or more and 4.0 mass% or less in total of one or more elements selected from Pd and Au, and 20 mass ppm or more and 500 mass ppm or less in total of one or more elements selected from among Ca, Y, La, Sm and Ce, with the remainder consisting of Ag and inevitable impurities, and has a tensile strength at room temperatures of 18-32 kgf/mmand a tensile strength in a furnace at 250°C of 14 kgf/mmor more. With the constitution, there is no practical problem in each evaluation of continuous bondability, thermal cycle tests, an evaluation of damages of a chip immediately below a first junction, electrical resistivity, an evaluation of wire flow in resin sealing, and sulfur resistance of a wire.

Description

  The present invention relates to nickel, palladium, and gold (Ni / Ni) on a semiconductor element in a semiconductor package such as a power IC, LSI, transistor, BGA (Ball Grid Array package), QFN (Quad Flat Non lead package), and LED (Light Emitting Diode). The present invention relates to a bonding wire for connecting a (Pd / Au) coated electrode or an Au coated electrode and a conductor wiring of a circuit wiring board such as a lead frame, a ceramic substrate, or a printed board by a ball bonding method.

  In the semiconductor package such as the BGA, for example, as shown in FIG. 1, a package substrate 3 is provided on a wiring board 1 via solder balls 2, and a semiconductor element is further provided on the package substrate 3 via a die bonding material 4. A (chip) 5 is provided and the semiconductor element 5 is sealed with a sealing material 6. The electrical connection between the electrode a of the semiconductor element 5 and the conductor wiring (terminal) c of the package substrate 3 in this semiconductor package is performed by the ball bonding method.

  Further, in the package of the LED which is one of the semiconductor elements, for example, as shown in FIG. 2, the LED 13 is provided on the case heat sink 11 via the die bonding material 12 and the phosphor e is mixed. The LED 13 is sealed with the material 14. The electrical connection between the electrode a of the LED 13 and the conductor wiring (terminal) c of the case electrode 15 in this package is performed by the ball bonding method as in the case of a semiconductor package such as BGA. In the figure, 16 is a resin case body.

  The connection methods by these ball bonding methods are generally in the form shown in FIGS. 3A to 3H. The wire W shown in FIG. 3A is inserted into the capillary 10a and a ball ( From the state where FAB (Free Air Ball) b is formed, the clamp 10b is opened, and the capillary 10a is lowered toward the electrode a on the integrated circuit element. At this time, the ball (FAB) b is captured in the capillary 10a.

When the molten ball b comes into contact with the target electrode a (when the capillary 10a reaches the electrode a), the capillary 10a grips the molten ball b and applies heat / load / ultrasonic waves to the molten ball b, whereby the molten ball b Is bonded to the electrode a by solid phase bonding to form a 1st bond and bonded to the electrode a (1st bonding, FIG. 3B).
If the 1st bond is formed, the capillary 10a moves up to a certain height (FIG. (C)) and then moves to a position directly above the conductor wiring c (FIGs. (D) to (e)). At this time, in order to form a stable loop, there is a case where a special movement is performed on the capillary 10a so that the wire W is attached with a “string” (see the solid line from the chain line in FIG. 4D).

  The capillary 10a that has reached directly above the conductor wiring c descends toward the conductor wiring c and presses the wire W against the conductor wiring (2nd target) c (FIGS. (E) to (f)). At the same time, heat, a load, and an ultrasonic wave are applied to the pressed portion, thereby deforming the wire W and joining the wire W onto the conductor wiring c, and a tail that secures the tail in the next step. A bond is formed (2nd junction, FIG. 5F).

  After forming both the bonds, the capillary 10a rises with the wire W remaining, and after securing a tail of a certain length at the tip of the capillary 10a, the clamp 10b is closed (by grabbing the wire W), and the tail The wire W is torn off from the bond portion ((g) in the figure).

  The capillary 10a stops when it rises to the required height, and the tip of the wire W secured at the tip of the capillary 10a is discharged (sparked) by applying a high voltage with the discharge rod g, and the wire is heated by the heat. W is melted, and the melted wire material is turned into a spherical ball b by the surface tension and hardens (FIG. 11 (h)).

  One cycle is completed by the above operation, and thereafter, the electrode a and the conductor wiring c are connected by the ball bonding method by the same operation.

As a material of the bonding wire (wire) W used in this ball bonding method, gold of 4N (purity: 99.99 mass% or more) to 2N is used. As described above, gold is frequently used because the shape of the gold ball b is a perfect sphere and the hardness of the gold ball b to be formed is appropriate, and the chip 5 is damaged by the load and ultrasonic wave during bonding. This is because reliable bonding is possible and the reliability is high.
On the other hand, in a semiconductor package such as a BGA, since the gold bonding wire W is expensive, it is replaced with an inexpensive copper (Cu) bonding wire. Furthermore, by covering the surface of the copper bonding wire with palladium (Pd) or the like, a Pd surface-coated copper bonding wire has been developed, which improves the 2nd bondability, which is a problem with the copper bonding wire, and improves the productivity. (Patent Document 1). Silver (Ag) bonding wires have also been developed and used in part. (Patent Documents 2, 3, and 4)

JP 2007-123597 A JP-A-57-194232 JP 58-6948 A JP-A-11-288896

Gold bonding wires are expensive. The copper bonding wire that is an alternative material is inexpensive, but the FAB is harder than the gold bonding wire, and if the tip of the electrode a is fragile, the risk of chip damage increases. In addition, the 2nd bondability is poor as compared with the gold bonding wire, and there is a problem in the continuous bonding property.
The Pd surface-coated copper bonding wire has better 2nd bondability and better continuous bondability than the copper bonding wire, but the FAB is harder than the copper bonding wire, which causes a problem of chip damage.

Conventionally, an Al alloy (Al-Si-Cu etc.) pad has been used for the electrode a of a semiconductor package such as a BGA. However, high temperature reliability, for example, reliability at 150 ° C. or higher is required. Have studied an electrode a coated with Ni / Pd / Au (nickel / palladium / gold). Further, it is necessary to reduce damage to the fragile chip 5.
There is a problem that the Pd surface-coated copper bonding wire is difficult to bond to the Ni / Pd / Au coated electrode a, and the copper bonding wire should be bonded under conditions that do not damage the fragile chip 5. Then, there is a problem that sufficient joining cannot be performed.

  Furthermore, conventionally, an LED 13 having an electrode a coated with Au is used in an LED package, and a gold bonding wire is used for connection to the electrode a. Since the cost cannot be reduced with this combination using gold, an inexpensive bonding wire is also desired for the LED 13. However, the copper bonding wire has difficulty in continuous bonding, and the Pd surface-coated copper bonding wire has a hard FAB, which may cause chip damage. Further, when a copper bonding wire or a Pd surface-coated copper bonding wire is used, since the bonding wire itself has a low reflectance, the wire portion becomes a shadow, so the brightness of the LED 13 itself may be lowered depending on the type of the LED 13.

Further, in the conventional silver bonding wire, it is common to discharge in an inert atmosphere by blowing nitrogen (N ₂ ) gas when forming the ball b. On the other hand, in Patent Documents 2 and 3, by adding Al (aluminum) or Mg (manganese) to Ag (silver), a ball b having a good shape even if discharged in the air without blowing N ₂ gas. It is described that can be obtained.
However, in recent years, in the BGA semiconductor package, since the electrodes a are smaller and the distance between the electrodes a is closer, it is necessary to obtain a more stable true spherical ball b. It is more preferable to discharge by blowing a general N ₂ gas. When this N ₂ gas is blown to discharge, the intrusion of oxygen from the surroundings can be prevented, but when the wire tip is melted, the added Al or Mg deprives oxygen from the silver oxide on the wire surface, and Al ₂ O ₃ or MgO can be formed. At this time, if a large amount of Al or Mg is contained, a large amount of this Al ₂ O ₃ or MgO is generated on the surface of the ball b, and hard Al ₂ O ₃ or MgO is formed during bonding with the electrode a. Has a problem of damaging the electrode a.

Similarly, in Patent Document 4, in order to improve wire strength and heat resistance, Ca (calcium), Sr (strontium), Y (yttrium), La (lanthanum), Ce (cerium), Eu (europium), Be ( It is described that elements such as beryllium), Ge (germanium), In (indium), and Sn (tin) are added. However, when these elements are added in a large amount, the hardness of the ball b increases and the electrode a Have problems to damage.
In Patent Document 4, Pt (platinum), Pd, Cu, Ru (ruthenium), Os (osmium), Rh (rhodium), Ir (iridium), and Au are added in order to increase the bonding reliability of the wire. It is described. However, if such an element is added in a large amount, the electric resistance of the wire itself is increased, resulting in a problem that the performance as the bonding wire W is impaired. That is, as described above, in a semiconductor package such as a BGA, the electrodes a are smaller and the distance between the electrodes a is closer, so that it is required to reduce the first junction. For this purpose, it is necessary to reduce the diameter of the bonding wire. However, if the electric resistance of the wire increases, there is a problem that the diameter of the wire cannot be reduced. In the LED 13, the operating current is increased to increase the luminance. However, if the electric resistance of the wire is high, a problem of heat generation occurs and a problem of shortening the life of the sealing resin occurs.

Furthermore, recently, the standard for reliability evaluation of semiconductor packages has become stricter, mainly for in-vehicle applications, and the demand for thermal shock resistance that repeats holding at low and high temperatures has been increasing.
When a semiconductor package assembled using the above-described silver wire is subjected to a more severe thermal cycle test, the wire may break due to the warpage of the substrate or the expansion and contraction of the resin.

  Incidentally, if the gold bonding wire is bonded to the Ni / Pd / Au coated electrode a or the Au coated electrode a, high thermal shock resistance can be obtained, but there is a problem that the material cost becomes expensive.

  The present invention has an object to provide a bonding wire that has good bonding properties with Ni / Pd / Au coated electrode a or Au coated electrode a, has excellent thermal shock resistance, and is cheaper than a gold bonding wire. And

To achieve the above object, the present invention provides a bonding wire for connecting a Ni / Pd / Au coated electrode of a semiconductor element or an Au coated electrode and a conductor wiring of a circuit wiring board by a ball bonding method. One or more elements selected from the group consisting of 1.0% by mass or more and 4.0% by mass or less, including one or more elements selected from Ca and rare earth elements in total of 20 mass ppm or more and 500 mass ppm or less. The balance is made of Ag and inevitable impurities, and the tensile strength of the wire (W) at room temperature is 18 kgf / mm ² or more and 32 kgf / mm ² or less, preferably 18 kgf / mm ² or more and 25 kgf / mm ² or less. tensile strength at high temperature tensile test of performing a tensile test at ℃ oven is 14 kgf / mm ² or more, more preferably 15 kgf / mm ² or more It was. At this time, the high-temperature tensile test in the 250 ° C. furnace is preferably performed at 250 ° C. as it is after heating the wire at 250 ° C. for 20 seconds.

The bonding wire mainly composed of Ag can be made cheaper than the bonding wire mainly composed of Au.
Incidentally, the bonding wire mainly composed of Ag has high corrosion resistance at the joint portion with the Ni / Pd / Au coated electrode or Au coated electrode, but the joint portion with the Al electrode has low corrosion resistance.

One or more elements selected from Pd and Au are added in order to obtain corrosion resistance and good electrical characteristics. If at least one element selected from Pd and Au is less than 1.0% by mass, the resistance to sulfidation of the wire may become a problem, and a substance that promotes sulfidation in the atmosphere or in the sealing resin (sulfurization) When hydrogen or the like is present, silver sulfide is generated on the surface of the wire, thereby reducing the reliability of the connection portion.
On the other hand, if an amount exceeding 4.0% by mass is added, the electric resistance of the wire becomes too high, and it becomes difficult to reduce the diameter of the wire.

One or more elements selected from Ca and rare earth elements are added in order to improve wire strength and heat resistance. However, if the content is less than 20 ppm by mass, the heat resistance of the wire is lowered and there is a practical problem. Arise. Moreover, when added exceeding 500 mass ppm, the hardness of the ball | bowl b will become high and the electrode a will be damaged at the time of 1st joining. Therefore, the total addition amount of at least one element selected from Ca and rare earth elements is 20 mass ppm or more and 500 mass ppm or less. More preferably, it is 20 mass ppm or more and 100 mass ppm or less, and if it is this range, the heat resistance of a wire is high and the damage degree of the electrode a at the time of 1st joining can also be restrained lower.
Here, since rare earth elements are difficult to obtain, addition of Ca is most preferable.

  The wire diameter of the wire W is arbitrary as long as it can be used as a bonding wire. If it is 50.8 μm or less, the molten ball b can be made smaller, and if it is less than 12 μm, it becomes difficult for an operator to pass the wire W through the capillary 10a before bonding, workability is deteriorated, and air pressure is applied to the wire by air pressure. Sufficient tension cannot be applied, and loop control may be difficult.

  Various methods can be adopted as the method for manufacturing the bonding wire W. For example, Ag having a purity of 99.99% by mass or more contains 1.0 to 4.0% by mass of one or more elements selected from Pd and Au. %, Ca, and one or more elements selected from rare earths are added in a total of 20 to 500 ppm by mass, and a rod having the chemical composition with a large wire diameter is produced by a continuous casting method, and the wire diameter is reduced to 50.8 μm or less. By sequentially penetrating, the wire is drawn to a predetermined wire diameter. Thereafter, the wire W is subjected to a tempering heat treatment.

The tempering heat treatment is a continuous heat treatment by drawing the wire W to a predetermined wire diameter and winding the wire W around the reel, running it in a tubular heat treatment furnace, and winding it again with a take-up reel. . In the tubular heat treatment furnace, N ₂ gas or a gas obtained by mixing a small amount of hydrogen with N ₂ is allowed to flow. The furnace temperature is 350 ° C. or more and 600 ° C. or less, and the heat treatment is performed at a wire traveling speed of 30 to 90 m / min. At this time, for example, if the furnace length is 50 cm, the tempering heat treatment time is 0.33 to 1 second when the wire traveling speed is 30 to 90 m / min.

The “room temperature tensile strength” of the bonding wire W is a value obtained by subjecting a sample having a length of 100 mm to a tensile test at room temperature of 15 to 25 ° C. and dividing the broken load of the wire W by the cross-sectional area.
The “high temperature tensile strength” of the bonding wire W is a sample having a length of 100 mm heated in a furnace at 250 ° C. and then subjected to a tensile test in a furnace at 250 ° C., and the broken load of the wire W is divided by the cross-sectional area. Indicates the value.
Here, if the room temperature tensile strength is less than 18 kgf / mm ² , the wire strength is insufficient, and a wire flow is generated in which the wire loop is deformed by the resin flowing in during resin sealing after wire bonding. Moreover, when it exceeds 32 kgf / mm < ² >, 2nd bondability will worsen and will cause a machine stop. More preferably, if it is 25 kgf / mm ² or less, 2nd bondability is high, and stable production is possible even at a low temperature setting such as a stage temperature of 150 ° C.
Further, if the high-temperature tensile strength is less than 14 kgf / mm ² , there is a problem in the life when the product after resin sealing is exposed to a thermal cycle test, but it is more preferably 15 kgf / mm ² or more. Thermal cycling characteristics are obtained.

In the tempering heat treatment, the furnace temperature was set to 350 ° C. or more and 600 ° C. or less, and the wire traveling speed was set to 30 to 90 m / min. This is because the wire W having a chemical composition such as 1.0 to 4.0% by mass can be adjusted so that the normal temperature tensile strength is 18 to 32 kgf / mm ² and the high temperature tensile strength is 14 kgf / mm ² or more. .

  Since the present invention is mainly composed of Ag as described above, it can be made cheaper than bonding wires mainly composed of Au, and can be appropriately added by adding appropriate amounts of Pd, Au, Ca, and rare earth elements. It becomes a wire of sufficient strength and can have good bondability with the Ni / Pd / Au coated electrode or Au electrode.

Schematic diagram of semiconductor package Schematic diagram of LED package It is explanatory drawing of a ball bonding method, (a)-(h) is the middle figure

  A silver alloy having a chemical composition shown in Table 1 was cast using high-purity Ag having a purity of 99.99% by mass or more (4N) to prepare an 8 mmφ wire rod. The wire rod was drawn into a silver alloy wire having a predetermined final wire diameter (12 to 50 μmφ) and continuously annealed at various heating temperatures and heating times in a nitrogen atmosphere. The tempering heat treatment by the continuous annealing was performed in a furnace having a furnace length of 50 cm at a furnace temperature of 350 ° C. or more and 600 ° C. or less and a wire traveling speed of 30 to 90 m / min. The chemical components were quantified by ICP-OES (high frequency inductively coupled plasma emission spectroscopy).

Each of the continuously annealed wires W was subjected to a tensile test at a room temperature of 15 to 25 ° C. to measure a room temperature tensile strength (kgf / mm ² ). In the tensile test, a wire W having a sample length of 100 mm was pulled at a tensile speed of 10 m / min, the breaking load at the time of breaking was measured, and the breaking load / cross-sectional area was calculated. In Table 1, the room temperature tensile strength is “room temperature breaking load”.
As for the tensile strength at 250 ° C., the wire W was heated in a furnace at 250 ° C. for 20 seconds, and kept at 250 ° C. as it was, pulled at a rate of 10 m / min. Measured and calculated as the breaking load / cross-sectional area. In Table 1, the tensile strength is “high temperature breaking load”.

The following tests were performed on each of the examples and comparative examples.
"Evaluation item"
About each wire W, the connection by the ball bonding method shown in FIG. 3 was performed with the automatic wire bonder. That is, an FAB (ball b) is produced at the tip of the wire W by arc discharge with the discharge rod g, and is bonded to the Ni / Pd / Au coated electrode a or the Au coated electrode a on the semiconductor elements (chips) 5 and 13. The other end of the wire was joined to a lead terminal (conductor wiring) c (see FIGS. 1 and 2). In addition, at the time of FAB production, arc discharge was performed while flowing nitrogen (N ₂ ) gas at the tip of the wire W. For the lead terminal c, an Ag-coated 42% Ni—Fe alloy was used.
Table 2 shows the continuous bonding property, thermal cycle test, chip damage at the first joint, electrical resistance, wire flow during resin sealing, sulfidation resistance of the wire, and overall evaluation in the bonding sample used for the evaluation. Their evaluation methods are as follows.

"Evaluation method"
(1) “Continuous bonding”
Bonding machine performs 10,000 continuous bonding, "A" if no machine stop occurs, "B" if one machine stop occurs, "D" if more than one machine stop occurs It was. At this time, if the stage temperature is lowered, the continuous bonding becomes difficult. Therefore, it was performed at two levels of 175 ° C. (± 5 ° C.) and 150 ° C. (± 5 ° C.).

(2) “Thermal cycle test”
After bonding, the resin-sealed semiconductor sample was evaluated using a commercially available thermal cycle test apparatus. The temperature history was 1000 cycles, with -40 ° C / 30 minutes to 125 ° C / 30 minutes as one cycle. Electrical tests were performed after the test to evaluate continuity. The number of wires evaluated is 500, and when the defect rate is 0, the resistance to the thermal cycle is high, so “A”, when the defect rate is 1% or less, “B”, when it exceeds 1%, it is resistant Is “D” because of low.

(3) “Evaluation of chip damage immediately after first bonding after bonding”
The 1st junction and the electrode film were dissolved with aqua regia, and the cracks of the semiconductor elements 5 and 13 were observed with an optical microscope and a scanning electron microscope (SEM). When 100 or less joints are observed and one or less minute pits of less than 3 μm are not found, “A”, and when 2 to 5 cracks of 3 μm or more are recognized, there is no problem in use. “B”, and when 5 or more cracks of 3 μm or more were observed, “D” was assigned.

(4) “Electric resistance”
The electric resistance at room temperature was measured using a four-terminal method. If the average of the resistivity of the three samples was 4.0 μΩ · cm or less, “A” was given, and if it exceeded 4.0 μΩ · cm, “D” was given.

(5) "Evaluation of wire flow during resin sealing"
Wire length: After a 5 mm bonding sample was sealed with an epoxy resin, the maximum wire flow amount was measured with an X-ray non-destructive observation apparatus. Twenty measurements were made, and the ratio of the average value divided by the wire length of 5 mm was taken as the wire flow rate. When the wire flow rate was less than 7%, “A” was evaluated, and when the wire flow rate was 7% or more, there was a practical problem, and the evaluation was “D”.

(6) “Sulfur resistance of wire”
A 5% ammonium sulfide solution was heated to 60 ° C. in a container, and the wire sample was left in a vaporized environment, and surface analysis after 5 minutes was measured by Auger spectroscopy (AES).
Auger spectroscopic analysis is performed by sputtering with Ar ions in the depth direction for a unit time, and the sulfur concentration is measured each time, and the thickness of the sulfide layer is reached until it reaches half the sulfur concentration of the outermost layer. It was. For the conversion of thickness, general SiO ₂ conversion was used. Here, when the thickness of the sulfide layer was 200 mm or less, “A” was evaluated, and when it exceeded 200 mm, there was a practical problem, and the evaluation was set to “D”.

"Comprehensive evaluation"
In each evaluation, “A” indicates that all are “A”, “B” indicates that “A” and “B” are mixed, and “D” indicates that there is at least “D”.

  In Tables 1 and 2, when the total of one or more elements selected from Ca, Y, Sm, La, and Ce exceeds 500 ppm by mass, the formation of precipitates on the FAB surface was confirmed from Comparative Examples 8 and 10. Since chip damage at the 1st joint occurs, “Chip damage at 1st joint” becomes “D”, and “D” also in the overall evaluation. On the other hand, if the total of these elements is less than 20 mass% ppm, the heat resistance is reduced from Comparative Examples 5, 6, and 9, and becomes “D” in the thermal cycle test and becomes “D” in the comprehensive evaluation. Yes.

  When the total of Pd and Au is less than 1.0% by mass, Comparative Example 1 indicates that the wire has a resistance to sulfidation of “D” and when 4.0% by mass is exceeded, Comparative Examples 8 to 10 indicate that In the evaluation of resistance, it is “D”, and both are “D” in the overall evaluation.

Furthermore, when the tensile strength at normal temperature (room temperature breaking load) is less than 18 kgf / mm ² , from Comparative Examples 1, 4, and 7, the evaluation of wire flow at the time of resin sealing becomes “D”, which is a comprehensive evaluation. “D”. On the other hand, if it exceeds 32 kgf / mm ² , the ^2nd bondability deteriorates from Comparative Examples 8 to 10, and the continuous bondability becomes “D”, which is “D” in the comprehensive evaluation.
Further, when the tensile strength (high temperature breaking load) in the tensile test in which the test is performed in a 250 ° C. furnace is less than 14 kgf / mm ² , the resistance to thermal cycle is obtained from Comparative Examples 2, 3, 5, 6, and 9. Low, “D” in the thermal cycle test and “D” in the overall evaluation.

On the other hand, in each of Examples 1 to 10, the total of Pd and Au is 1.0 to 4.0% by mass, and the total of one or more elements selected from Ca, Y, Sm, La, and Ce. since but 20 mass ppm or more, including 500 mass ppm or less, and the tensile strength at tensile test tensile strength at room temperature is carried out a test in 18~32kgf ^/ mm 2, 250 ℃ oven is 14 kgf / mm ² or more, Obtain "A" or "B" in continuous bonding, thermal cycle test, evaluation of chip damage just below the 1st junction, electrical resistance, evaluation of wire flow during resin sealing, and evaluation of sulfidation resistance of wires. In the comprehensive evaluation, “B” or more is obtained, and it is understood that there is no practical problem.

Moreover, if it contains 1 or more types of elements chosen from Ca, Y, Sm, La, and Ce and the sum total is 100 mass ppm or less, Examples 1-3, 5-7, 9, and Comparative Examples 1-3 , 6, 7, and 9 are “A” in the evaluation of chip damage immediately below the 1st junction, and it can be understood that the chip has high reliability. Furthermore, when the tensile strength at room temperature is 18 to 25 kgf / mm ² , “A” in continuous bonding property evaluation at 150 ° C. from Examples 1, 2, 5 to 7 and Comparative Examples 2, 3, 5, and 6. Thus, it can be understood that good workability at a low stage temperature can be obtained. Further, when the tensile strength in a 250 ° C. furnace is 15 kgf / mm ² or more, from Examples 2, 4, 5, 7, 9, 10, and Comparative Examples 1, 7, 8, 10, A ”.

From the above, one or more elements selected from Pd and Au in total are 1.0 mass% or more and 4.0 mass% or less, and one or more elements selected from Ca and rare earth elements are total 20 mass ppm or more. , 500 ppm by mass or less, the balance is made of Ag and inevitable impurities, the tensile strength of the wire W at room temperature is 18 to 32 kgf / mm ² , and the wire is heated as it is for 20 seconds in a furnace at 250 ° C. When the tensile strength in a tensile test conducted in a furnace at 14 ° C. is 14 kgf / mm ² or more, continuous bonding property, thermal cycle test, evaluation of chip damage immediately below the 1st joint, electrical resistance, wire during resin sealing In each evaluation of flow and sulfidation resistance of the wire, there is no practical problem, and the content of one or more elements selected from Ca and rare earth elements is 20 mass ppm. On, if it is 100 mass ppm or less, it becomes to have high reliability is "A" in the evaluation of the chip damage just below 1st junction, the tensile strength at room temperature is at 18~25kgf / mm ^2, In continuous bondability evaluation at 150 ° C., “A” is obtained, and good workability can be obtained. Further, when the tensile strength in a 250 ° C. furnace is 15 kgf / mm ² or more, resistance to thermal cycle is high. It will be a thing.

3, 15 Circuit wiring board 5 Semiconductor element 13 LED
W Bonding wire a Semiconductor element (LED) electrode b Molten ball b ′ Crimp ball c Circuit wiring board conductor wiring (lead terminal)

Claims (4)

For connecting the Ni / Pd / Au coated electrode (a) or the Au coated electrode (a) of the semiconductor element (5, 13) and the conductor wiring (c) of the circuit wiring board (3, 15) by a ball bonding method. A bonding wire (W),
A total of one or more elements selected from Pd and Au is 1.0% by mass or more and 4.0% by mass or less, and a total of one or more elements selected from Ca and rare earth elements is 20% by mass or more and 500% by mass. Contains ppm or less,
The balance consists of Ag and inevitable impurities,
The wire (W) has a tensile strength at room temperature of 18 to 32 kgf / mm ² , and after heating the wire in a 250 ° C. furnace, the tensile strength in a tensile test in which the test is performed in a 250 ° C. furnace is 14 kgf. / Mm ² or more of bonding wire,   2. The bonding wire according to claim 1, wherein the content of one or more elements selected from Ca and rare earth elements in the wire (W) is 20 mass ppm or more and 100 mass ppm or less. The bonding wire according to claim 1 or 2, wherein the wire (W) has a tensile strength at room temperature of 18 to 25 kgf / mm ² . The bonding wire according to any one of claims 1 to 3, wherein the wire (W) has a tensile strength in a furnace at 250 ° C of 15 kgf / mm ² or more.

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