GB2273716A - Bonding wire for semiconductor device - Google Patents

Bonding wire for semiconductor device Download PDF

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Publication number
GB2273716A
GB2273716A GB9401294A GB9401294A GB2273716A GB 2273716 A GB2273716 A GB 2273716A GB 9401294 A GB9401294 A GB 9401294A GB 9401294 A GB9401294 A GB 9401294A GB 2273716 A GB2273716 A GB 2273716A
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United Kingdom
Prior art keywords
boiling point
low boiling
atppm
bad
point element
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Granted
Application number
GB9401294A
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GB2273716B (en
GB9401294D0 (en
Inventor
Katsuyuki Toyofuku
Ichiro Nagamatsu
Shinji Shirakawa
Hiroto Iga
Takeshi Kujiraoka
Kensei Murakami
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Tanaka Denshi Kogyo KK
Original Assignee
Tanaka Denshi Kogyo KK
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Priority claimed from JP2146498A external-priority patent/JP2888252B2/en
Priority claimed from JP2146499A external-priority patent/JPH0438841A/en
Priority claimed from GB9111994A external-priority patent/GB2245902B/en
Application filed by Tanaka Denshi Kogyo KK filed Critical Tanaka Denshi Kogyo KK
Publication of GB9401294D0 publication Critical patent/GB9401294D0/en
Publication of GB2273716A publication Critical patent/GB2273716A/en
Application granted granted Critical
Publication of GB2273716B publication Critical patent/GB2273716B/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/42—Wire connectors; Manufacturing methods related thereto
    • H01L24/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L24/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/04—Alloys based on a platinum group metal
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    • H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L24/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
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    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
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  • Engineering & Computer Science (AREA)
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  • Wire Bonding (AREA)

Abstract

The wire contains high purity Pd or Pd alloy as a base metal and 25 - 1000 atppm of low boiling point element 1 e.g. Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb having a boiling point lower than a melting point of said base metal and soluble in liquid Pd and/or 5 - 500 atppm or low boiling point element 11 e.g. P, S, As, Te having a boiling point lower than the melting point of said base metal and insoluble in liquid Pd under the condition of (content of element 1)/25+ (content of element 11)/5>/=1>/= (content of element 1)/1000+ (content of element 11)/500.

Description

BONDING WIRE FOR SEMICONDUCTOR DEVICE BACKGROUND OF THE INVENTION The present invention relates to a bonding wire for a semiconductor device adapted to be used for connection between a chip electrode of the semiconductor device and an external lead, and more particularly to such a bonding wire suitable for a ball bonding process.
It is known that a chip electrode of a semiconductor device is connected through a bonding wire such as Au wire to an external lead by melting a tip of the Au wire depending from an end of a capillary by means of an electrical torch to form a ball at the tip of the Au wire, pressing the ball against the chip electrode to bond together, the leading the Au wire to the external lead so as to form a loop, bonding the loop to the external lead, and finally cutting the Au wire.
In such a conventional bonding wire for a semiconductor device, however, a neck portion formed immediately above the ball is influenced by heat upon formation of the ball to relax a stress accumulated in the wire. Accordingly, a mechanical strength of the neck portion becomes lower than that of a base wire when not influenced by heat. As a result, the neck portion is ruptured, or wire falling or wire sagging is generated during a bonding operation.
Furthermore, in a temperature life cycle test of products, a stress is generated by heat expansion and contraction due to a repeated temperature change, and the stress is concentrated at the neck portion, causing a problem in that the rupture of the neck portion is easily generated.
In recent years, high-density mounting of LSI has accompanied a marked tendency to provide a multiplicity of pins. In this circumstance, it is necessary to reduce the diameter of the bonding wire and thereby reduce the bonding pitch.
However, as the neck portion of the aforementioned bonding wire easily ruptures, it is impossible to reduce the diameter of the bonding wire, and the above necessity cannot accordingly be met.
SUMMARY OF THE INVENTION It is accordingly an object of the present invention to make the strength of the neck portion equal to or more than that of the base wire.
According to the present invention which achieves the above object, there is provided a bonding wire for a semiconductor device, containing high purity Pd or Pd alloy as a base metal and 25 - 10000 atppm of low boiling point element/elemental mixture (I) which has a boiling point lower than the melting point of said base metal and which is soluble in liquid Pd and wherein said low boiling point element/elemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb, or there is provided a bonding wire for a semiconductor device, containing high purity Pd or Pd alloy as a base metal and 5 - 500 atppm of low boiling point element/elemental mixture (II) which has a boiling point lower than the melting point of said base metal and which is insoluble in liquid Pd wherein said low boiling point element (II) contains at least one of P, S, As or T1, or there is provided a bonding wire for a semiconductor device, containing high purity Pd or Pd alloy as a base metal and 5 10000 atppm of a mixture of low boiling point element/elemental mixture (I) which has a boiling point lower that the melting point of said base metal and which is soluble in liquid Pd and wherein said low boiling point element/elemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb and low boiling point element/elemental mixture (II) which has a boiling point lower than the melting point of said base metal and which is insoluble in liquid Pd wherein said low boiling point element (II) contains at least one of P, S, As or T1 under the condition of (content of said low boiling point element/elemental mixture (I) atppm)/25 + (content of said low boiling point element/elemental mixture (II) atppm)/5 2 1 2 (content of said low boiling point element/elemental mixture (I) atppm)/10000 + (content of said low boiling point element/elemental mixture (II) atppm)/500.
The aforementioned high purity Pd contains 99.9% or more of Pd and a residual amount of unavoidable impurities.
The aforementioned Pd alloy preferably contains said high purity Pd and at least one of Au, Ag; Pt, Rh, Ru, Os, Ir, Cu, Mo, Fe and Ti and most preferably comprises the high purity Pd and at least one of Au (10 at% or less), Ag (5 at% or less), Pt (20 at% or less), Rh (8 at% or less), Ru, Os, Ir (1 at% or less), Cu, Mo, Fe, Ti (1 atppm - 5 at%).
The use of this Pd alloy improves the mechanical strength of the base metal itself at both ordinary and high temperatures to thereby enabling high-speed bonding, and also preventing enlargement of crystal grain in the neck portion upon formation of the ball.
The content of each component of the bonding wire for the semiconductor device according to the present invention is limited for the following reasons.
The low boiling point elements/elemental mixture(s), which have boiling points lower than the melting point of the base metal, are vaporized and scattered from the molten ball upon formation thereof. However, low boiling point element/elemental mixture (I) cannot be vaporized from the neck portion, but tends to be vaporized in the neck portion to generate a stress. The main reason for this is because element/elemental mixture (I) is soluble in liquid Pd it is difficult for it to escape from liquid Pd.
Accordingly, if the content of the low boiling point element/elemental mixture (I) is less than 25 atppm, a satisfactory characteristic cannot be obtained. In contrast, if the content of the low boiling point element/elemental mixture (I) is more than 10000 atppm, embrittlement of the base wire appears to cause a difficulty of wire drawing.
Moreover, if the amount of element/elemental mixture (i) residing in the ball upon formation thereof becomes large the ball is excessively hardened, causing chip cracking upon bonding.
For the above reasons, the content of the low boiling point element/elemental mixture (I) needs to be set in the range of 25 - 10000 atppm On the other hand, low boiling point element/elemental mixture (II) which is insoluble in liquid Pd may easily escape from liquid Pd. Accordingly, if the content of the low boiling point element/elemental mixture (II) is less than 5 atppm, a satisfactory characteristic cannot be obtained.
In contrast, if the content of the low boiling point element/elemental mixture (II) is more than 500 atppm, embrittlement of the base wire appears to cause a difficulty of wire drawing.
Moreover, when an amount of the element/elemental mixture (II) not scattered from the ball but residing in the ball upon formation thereof becomes large the ball is excessively hardened, causing chip cracking upon bonding.
For the above reasons, the content of the low boiling point element/elemental mixture (II) needs to be set in the range of 5 - 500 atppm.
Under the condition of (content of said low boiling point element/elemental mixture (I) atppm)/25 + (content of said low boiling point element/elemental mixture (II) atppm)/5 2 1, if the lower limit of the total content of the low boiling point eiement/elemental mixture (I) soluble in liquid Pd and the low boiling point element/elemental mixture (II) insoluble in liquid Pd is less than 5 atppm, a satisfactory characteristic cannot be obtained. Therefore, the lower limit of the total content of both the elements/elemental mixture s (I) and (II) under the above condition needs to be set to 5 atppm.
Further, under the condition of (content of the low boiling point element/elemental mixture (I) atppm)/10000 + (content of the low boiling point element/elemental mixture (II) atppm)/500 < 1, if the upper limit of the total content of the low boiling point element/elemental mixture (I) which is soluble in liquid Pd and the low boiling point element/elemental mixture (II) which is insoluble in liquid Pd is more than 10000 atppm, embrittlement of the base wire appears to cause a difficulty of wire drawing.
Moreover, when the amount of the elements/elemental mixtures (I) and (II) not scattered from the ball, but residing in the ball upon formation thereof, becomes large the ball becomes excessively hardened, causing chip cracking upon bonding. Therefore, the upper limit of the total content of both the elements/elemental mixtures (I) and (II) needs to be set at 10000 atppm.
Consequently, the bonding wire of the present invention contains high purity liquid Pd or Pd alloy as a base metal and 25 - 10000 atppm of low boiling point element/elemental mixture (I), or contains high purity Pd or Pd alloy as a base metal and 5 - 500 atppm of low boiling point element/elemental mixture (II) or contains high purity Pd or Pd alloy as a base metal and 5 - 10000 atppm of a mixture of low boiling point element/elemental mixture (I) and low boiling point element/elemental mixture (II) under the condition of (content of said low boiling point element/elemental mixture (I) atppm)/25 + (content of said low boiling point element/elemental mixture (II) atppm)/5 2 1 2 (content of said low boiling point element/elemental mixture (T) atppm)/10000 + (content of said low boiling point element/elemental mixture (II) atppm) /500.
With this constitution, upon melting the tip of the wire prior to bonding the low boiling point element(s)/elemental mixture(s) in the ball are mostly vaporized and scattered upon formation of the ball thus preventing gas absorption peculiar to metal. This provides a satisfactory ball for bonding.
However, the low boiling point element(s)/elemental mixture(s) in the neck portion cannot be vaporized from the surface thereof, because the neck portion is at a lower temperature than the ball portion, resulting in a higher viscosity and greater resistance therefore they tend to be vaporised in the neck portion which generate a stress.
Accordingly, the rupture strength of the neck portion after bonding is improved as compared with that of the base wire generating no stress.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS There will now be described some preferred embodiments of the present invention.
In a preferred embodiment employing high purity Pd or Pd alloy as the base metal, various samples were prepared in the following manner. The base metal used was high purity Pd having a purity of 99.95%, Pd alloy containing the high purity Pd and 10 at% of Au, Pd alloy containing the high purity Pd and 5 atppm of Ag, Pd alloy containing the high purity Pd and 0.5 at % of Mo, and Pd alloy containing the high purity Pd and 6 at % of Cu. Then, at least one of Zn, Cd, Hg, P and S was added to the high purity Pd and the Pd alloys prepared above, and these mixtures were molten to be cast.
The castings thus obtained were then subjected to a grooved roll, during which they were annealed. Then, they were subjected to wire drawing, thereby forming base wires each having a diameter of 30 um. Thereafter, further stress relieving was sufficiently conducted to finally obtain the samples.
The contents of the additional elements in the samples are shown in Table 1. In Table 1, Nos 1 - 54 of the samples correspond to the preferred embodiment, and Nos 55 and 56 of the samples correspond to comparisons departing from the composition range according to the present invention.
By using the above samples, a pull test was carried out a given number of times (n = 40), and measurements were carried out for a pull strength, number of times of rupture of the base wire rather than the neck portion, condition of workability, and existence of chip crack. The result of the measurements for the high purity Pd and each Pd alloy is shown in Table 2.
TABLE (1)
SAM?L ADDITIONAL ELEMENT (;t ppm) Na Xn Cd Hg P S 1 20 2 25 3 50 4 500 H i z 5 jug00 I 6 10000 a 7 11000 o 8 20;; 8 20 9 25 o 10 50 111 soo I cm 2 ill 1 12 i 5000 I 151 20 16 25 17 50
18 500 19 5000 20 10000 21 11000 22 3 23 5 H z 24 50 2j 500 G 26 6 0 0 0 o 27 3 .2 28 5 29 50 30 500 us 31 . j 600 c 32 --------- ---------- ---------- ----- 10 10 Ç 33 100 100 34 1000 1000 35 5000 50(F0 36 6000 6000 31 10 10 10
- 38 100 100 100 39 1000 1000 1000 40 5000 5000 5000 41 2 3 H 42 = 5 1 5 43 50 1 ------------------ 50 w 63 sO 50 - 44 100 100 n o 45 -------- ---------------- l 250 250 2 46 250 300 I47 10 2 a 48 10 10 2 - I cK 49 10 2 2 X 50 10 250 250 51 1000 1000 200 200 cw 52 1000 1000 10 2001 200 53 2000 2000 2000 0 50 | 50 54 3000 3000 3000 50 50 z 0 55 Au (99. 99 ) 2 56 Cu (99. 9999 C TABLE (2)
Pd Pd + Au ((10at%) Pd + Ag (5 at%) Pd + Mo (0, 5at %) Pd + Cu (5 at96) PULL C MODE WORKA- CHIP PULL C MODE WORKA- CHIP PULL C MODE WORKA- CHIP PULL C MODE RORAK- CHIP PULL C MODE WORKA- CHIP STREN- RUPTUEE BILITY CRACK STREN- RUPTURE BILTY CRACK STREN- RUPTURE BLITY CRACK STREN- RUPTURE BILITY CRACK STREN- RUPTURE BILITY CRACK GTH (g) (n-40) GTH (g) (n-40) GTH (g) (n-40) GTH (g) (n-40) GTH (g) (n-40) 1 19.0 4 GOOD @@@@@ 21.3 7 GOOD @@@@@ 21.5 6 GOOD @@@@@ 20.0 8 GOOD @@@@@ 20.0 1 GOOD @@@@@ 2 19.0 22 " " 21.3 25 " " 21.5 22 " " 20.1 26 " " 22.0 23 " " 3 19.2 27 " " 21.4 29 " " 21.5 30 " " 20.1 29 " " 22.1 27 " " 4 19.7 35 " " 21.5 32 " " 21.6 33 " " 20.2 32 " " 22.1 31 " " 5 19.9 33 " " 21.6 31 " " 21.7 34 " " 20.5 34 " " 22.2 33 " " 6 20.1 35 " " 21.7 34 " " 21.7 34 " " 20.6 31 " " 22.4 35 " " 7 20.2 30 BAD " 21.7 33 BAD @@@@@ 21.8 32 BAD @@@@@ 20.7 31 BAD @@@@@ 22.4 32 BAD @@@@@ 8 19.0 5 GOOD " 21.3 7 GOOD @@@@@ 21.5 6 GOOD @@@@@ 20.0 8 GOOD @@@@@ 22.0 4 GOOD @@@@@ 9 19.1 21 " " 21.3 23 " " 21.5 21 " " 20.0 25 " " 22.1 23 " " 10 19.2 27 " " 21.4 25 " " 21.6 27 " " 20.1 34 " " 22.1 29 " " 11 19.7 36 " " 21.5 32 " " 21.6 33 " " 20.2 38 " " 22.2 29 " " 12 20.0 35 " " 21.5 35 " " 21.7 37 " " 20.6 36 " " 22.3 34 " " 13 20.1 32 " " 21.6 33 " " 21.7 34 " " 20.6 33 " " 22.4 33 " " 14 20.3 31 BAD " 21.6 35 BAD @@@@@ 21.8 36 BAD @@@@@ 20.7 32 BAD @@@@@ 22.4 35 BAD @@@@@ 15 19.1 4 GOOD " 21.2 7 GOOD @@@@@ 21.4 5 GOOD @@@@@ 20.0 10 GOOD @@@@@ 22.0 6 GOOD @@@@@ 16 19.1 23 " " 21.3 27 " " 21.5 22 " " 20.0 26 " " 22.1 22 " " 17 19.2 30 " " 21.4 33 " " 21.6 28 " " 20.2 34 " " 22.1 30 " " 18 19.5 38 " " 21.6 39 " " 21.7 36 " " 20.3 37 " " 22.2 38 " " 19 19.9 37 " " 21.6 39 " " 21.7 37 " " 20.5 36 " " 22.2 35 " " 20 20.2 38 " " 21.7 36 " " 21.7 34 " " 20.6 33 " " 22.4 34 " "
21 20.3 33 BAD @@@@@ 21.7 35 BAD @@@@@ 21.8 31 BAD @@@@@ 20.7 35 BAD @@@@@ 22.4 36 BAD @@@@@ 22 19.0 12 GOOD " 21.3 10 GOOD @@@@@ 21.5 9 GOOD @@@@@ 20.0 13 GOOD @@@@@ 22.0 11 GOOD @@@@@ 23 19.1 21 " " 21.3 21 " " 21.5 20 " " 20.1 24 " " 22.0 23 " " 24 19.3 33 " " 21.4 29 " " 21.5 31 " " 20.2 37 " " 22.0 32 " " 25 19.6 37 " " 21.5 35 " " 21.5 36 " " 20.4 38 " " 22.1 35 " " 26 19.7 35 BAD " 21.6 36 BAD " 21.6 33 BAD " 20.4 36 BAD " 22.1 33 BAD " 27 19.0 10 GOOD " 21.3 10 GOOD " 21.5 12 GOOD " 20.0 10 GOOD " 22.0 9 GOOD " 28 19.2 22 " " 21.3 20 " " 21.5 31 " " 20.0 22 " " 22.0 21 " " 29 19.3 30 " " 21.3 27 " " 21.5 28 " " 20.1 30 " " 22.0 27 " " 30 19.6 36 " " 21.4 32 " " 21.6 31 " " 20.3 36 " " 22.1 32 " " 31 19.7 37 BAD " 21.5 36 BAD " 21.6 35 " " 20.4 38 " " 22.1 35 BAD " 32 19.1 6 GOOD " 21.3 3 GOOD " 21.5 3 " " 20.0 5 " " 22.0 4 GOOD " 33 19.2 22 " " 21.4 23 " " 21.5 24 " " 20.1 25 " " 22.0 22 " " 34 19.8 28 " " 21.5 29 " " 21.6 30 " " 20.4 33 " " 22.1 30 " " 35 20.1 35 " " 21.6 32 " " 21.7 33 " " 20.6 37 " " 22.4 35 " " 36 20,3 36 BAD " 21.6 34 BAD @@@@@ 21.8 35 " @@@@@ 20.7 35 BAD @@@@@ 22.4 33 BAD @@@@@ 37 19.2 27 GOOD " 21.4 26 GOOD @@@@@ 21.5 30 " @@@@@ 20.1 31 GOOD @@@@@ 22.1 32 GOOD @@@@@ 38 19.5 38 " " 21.5 37 " " 21.6 35 " " 20.1 39 " " 22.1 38 " " 39 19,8 37 " " 21.5 37 " " 21.6 36 " " 20.3 38 " " 22.1 37 " " 40 20.4 33 BAD " 21.6 36 BAD @@@@@ 21.8 33 BAD @@@@@ 20.7 38 BAD @@@@@ 22.4 35 BAD @@@@@ 41 19.1 23 GOOD " 21.3 21 GOOD @@@@@ 21.5 23 GOOD @@@@@ 20.1 25 GOOD @@@@@ 22.0 34 GOOD @@@@@ 42 19.3 29 " " 21.3 32 " " 21.5 28 " " 20.0 33 " " 22.0 30 " " 43 19.4 38 " " 21.3 37 " " 21.5 36 " " 20.2 38 " " 22.0 35 " " 44 19.5 37 " " 21.3 35 " " 21.5 38 " " 20.2 38 " " 22.0 36 " " 45 19.6 36 " " 21.5 34 " " 21.5 31 " " 20.4 37 " " 22.1 37 " "
46 19.1 36 BAD @@@@@ 21.5 35 BAD @@@@@ 21.5 36 BAD @@@@@ 20.3 37 BAD @@@@@ 22.1 37 BAD @@@@@ 47 19.1 6 GOOD " 21.3 7 GOOD " 21.5 7 GOOD " 20.1 9 GOOD " 22.0 6 GOOD " 48 19.2 20 " " 21.3 22 " " 21.5 21 " " 20.1 24 " " 22.0 23 " " 49 19.2 24 " " 21.4 26 " " 21.5 25 " " 20.1 28 " " 22.0 27 " " 50 19.5 37 BAD " 21.5 37 BAD " 21.5 36 BAD " 20.3 38 BAD " 22.1 37 BAD " 51 19.7 36 GOOD " 21.6 35 GOOD " 21.6 36 GOOD " 20.4 37 GOOD " 22.1 37 GOOD " 52 19.8 38 BAD " 21.6 37 BAD " 21.6 38 BAD " 20.4 38 BAD " 22.1 38 BAD " 53 20.1 38 GOOD " 21.6 38 GOOD " 21.7 39 GOOD " 20.5 39 GOOD " 22.2 38 GOOD " 54 20.2 37 BAD " 21.7 38 BAD @@@@@ 21.7 37 BAD @@@@@ 20.6 39 BAD @@@@@ 22.3 39 BAD @@@@@ PULL STRENGTH (g) C MODE RUPTURE (n = 40) 55 12 2 56 21 2 One very pertinent measurement which clearly exemplifies the strength of the neck portion of the wire of the invention is the number of C Mode Ruptures ie. the number of times the base wire ruptures at a point distant from the neck in a pull strength test of a bonded wire.In normal circumstances the vast majority of wires rupture in the neck region because this is the weakest point.
As can be seen from Table 2., it is appreciated that the number of times of C mode rupture in the pull test by using the samples according to the present invention is larger than that by using the samples in the comparisons outside the composition range according to the present invention, and that the neck portion is Stronger than the other portion of the base wire. Accordingly, it is understood that the abovementioned composition range according to the present invention is optimum.
In summary, the present invention has the following advantages.
(1) The bonding wire according to the second aspect of the present invention contains high purity Pd or Pd alloy as a base metal and 25 - 10000 atppm of low boiling point element/elemental mixture (I) having a boiling point lower than the melting point of said base metal and soluble in liquid Pd, and wherein said low boiling point elementielemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb or contains high purity Pd or Pd alloy as a base metal and 5 - 500 atppm of low boiling point element/elemental mixture (II) having a boiling point lower than the melting point of said base metal and insoluble in liquid Pd wherein said low boiling point element (II) contains at least one of P, S, As or T1, or contains high purity Pd or Pd alloy as a base metal and 5 - 10000 atppm of a mixture of low boiling point element (I) having a boiling point lower than the melting point of said base metal and soluble in liquid Pd and wherein said low boiling point element/elemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb and low boiling point element (II) having a boiling point lower than the melting point of said base metal and insoluble in liquid Pd wherein said low boiling point element (II) contains at least one of P, S, As or T1 under the condition of (content of said low boiling point element (I) atppm)/25 + (content of said low boiling point element (II) atppm)/5 2 1 2 (content of said low boiling point element (I) atppm)/10000 + (content of said low boiling point element (II) atppm)/500.
With this constitution, upon melting the tip of the wire prior to bonding the low boiling point element(s)/elemental mixtures in the ball formed are mostly is vaporized and scattered upon formation of the ball thus preventing gas absorption peculiar to metal. This provides a satisfactory ball for bonding.
However, the low boiling point element(s)/elemental mixture(s) which are in the neck portion cannot be vaporized from the surface thereof, because the neck portion is at a lower temperature than the ball portion, resulting in a higher viscosity and greater resistance therefore they tenfd to vaporised in the neck portion which generates a stress.
Accordingly, the rupture strength of the neck portion after bonding is improved as compared with that of the base wire generating no stress. Accordingly, the strength of the neck portion can be made equal to or more than that of the base wire.
In comparison with the prior art wherein the strength of the neck portion becomes less than that of the base wire because of influence of heat upon formation of the ball, the bonding wire of the present invention does not generate rupture of the neck portion, wire falling or wire sagging during the bonding operation. Furthermore, in the products temperature life cycle test a stress generated by repeated temperature changes is dispensed to be absorbed in the whole of the base wire. Accordingly, the rupturing of the neck portion which is where the bonding wire is most frequently ruptured can be greatly reduced to improve reliability of the bonding method.
(2) In view of the fact that with wires of the present invention rupturing of the neck portion is, compared with prior art wires, difficult to achieve, the diameter of the bonding wire can be greatly reduced thereby enabling a reduction in bonding pitch and realizing high density mounting of LSI.

Claims (6)

WHAT IS CLAIMS IS:
1. A bonding wire for a semiconductor device containing high purity Pd or Pd alloy as a base metal and 25 - 10000 atppm of low boiling point element/elemental mixture (I) which has a boiling point lower than the melting point of said base metal and which is soluble in liquid Pd and wherein said low boiling point element/elemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb.
2. A bonding wire for a semiconductor device, containing high purity Pd or Pd alloy as a base metal and 5 - 500 atppm of low boiling point element/elemental mixture (II) which has a boiling point lower than the melting point of said base .metal and which is insoluble n liquid Pd, wherein said low boiling point element (II) contains at least one of P, S, As or T1.
3. A bonding wire for a semiconductor device, containing high purity Pd or Pd alloy as a base metal and 5 - 10000 atppm of a mixture of low boiling point element/elemental mixture (I) which has a boiling point lower than the melting point of said base metal and which is soluble in liquid Pd and wherein said low boiling point element/elemental mixture (I) contains at least one of Zn, Cd, Hg, Li, Be, Mg, Sb, Te, Bi or Yb low boiling point element/elemental mixture (II) which has a boiling point lower than the melting point of said base metal and which is insoluble in liquid Pd, wherein said low boiling point element (II) contains at least one of P, S, As or T1 under the condition of (content of said low boiling point element/elemental mixture (I) atppm)/25 + (content of said low boiling point element/elemental mixture (II) atppm)/5 2 1 2 (content of said low boiling point element/elemental mixture (I) atppm)/10000 + (content of said low boiling point element/elemental mixture (II) atppm)/500.
4. A bonding wire in accordance with any preceding claim wherein said high purity Pd is at least 99.9% pure.
5. The bonding wire as defined in any of claims 1-3 wherein said Pd alloy contains said high purity Pd and at least one of Au, Ag, Pt, Rh, Ru, Os, Ir, Cu, Mo, Fe and Ti.
6. A bonding wire in accordance with claims 1, 2, 3 or 5 wherein said Pd alloy comprises the high purity Pd and at least one of Au (10 at% or less), Ru, Os, Ir (1 at% or less), Cu, Mo, Fe, Ti (1 atppm - 5 at%).
GB9401294A 1990-06-04 1994-01-24 Bonding wire for semiconductor device Expired - Fee Related GB2273716B (en)

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JP2146498A JP2888252B2 (en) 1990-06-04 1990-06-04 Bonding wire for semiconductor device
JP2146499A JPH0438841A (en) 1990-06-04 1990-06-04 Bonding wire for semiconductor element
GB9111994A GB2245902B (en) 1990-06-04 1991-06-04 Bonding wire for semiconductor device

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010017894A2 (en) * 2008-08-12 2010-02-18 W.C. Heraeus Gmbh Metal fibres for catalyst nonwovens

Citations (1)

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Publication number Priority date Publication date Assignee Title
JPS59177339A (en) * 1983-03-28 1984-10-08 Mitsubishi Metal Corp Fine pd alloy wire for wire-bonding of semiconductor device

Patent Citations (1)

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Publication number Priority date Publication date Assignee Title
JPS59177339A (en) * 1983-03-28 1984-10-08 Mitsubishi Metal Corp Fine pd alloy wire for wire-bonding of semiconductor device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010017894A2 (en) * 2008-08-12 2010-02-18 W.C. Heraeus Gmbh Metal fibres for catalyst nonwovens
WO2010017894A3 (en) * 2008-08-12 2010-06-10 W.C. Heraeus Gmbh Metal fibres for catalyst nonwovens
CN102123803A (en) * 2008-08-12 2011-07-13 W.C.贺利氏有限公司 Metal fibres for catalyst nonwovens
US8293678B2 (en) 2008-08-12 2012-10-23 Heraeus Materials Technology Gmbh & Co. Kg Metal fibers for catalyst non-wovens
AU2009281449B2 (en) * 2008-08-12 2013-02-07 Heraeus Materials Technology Gmbh & Co Kg Metal fibres for catalyst nonwovens
DE102008038611B4 (en) * 2008-08-12 2014-12-24 Heraeus Materials Technology Gmbh & Co. Kg Metal fibers for catalyst nonwovens

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