JP2007266310A - Sorting method of bonding wire, and managing method of diamond die for bonding wire - Google Patents

Sorting method of bonding wire, and managing method of diamond die for bonding wire Download PDF

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JP2007266310A
JP2007266310A JP2006089531A JP2006089531A JP2007266310A JP 2007266310 A JP2007266310 A JP 2007266310A JP 2006089531 A JP2006089531 A JP 2006089531A JP 2006089531 A JP2006089531 A JP 2006089531A JP 2007266310 A JP2007266310 A JP 2007266310A
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wire
cross
moment
diameter
value
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JP3905914B1 (en
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Mitsuo Takada
満生 高田
Toshitaka Mimura
利孝 三村
Hiroyuki Amano
裕之 天野
Yuichi Hirata
勇一 平田
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Tanaka Denshi Kogyo KK
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Tanaka Denshi Kogyo KK
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Priority to TW096109830A priority patent/TWI337774B/en
Priority to MYPI20070471A priority patent/MY145553A/en
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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Wire Bonding (AREA)
  • Wire Processing (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the generation of any leaning faultiness in bonding processes, by judging whether the leanings of extra-fine gold bonding wires are good or bad before their connections. <P>SOLUTION: In a sorting method of bonding wires the whole circumference of a bonding wire before its connection is divided finely, and the wire diameters of the divided circumferential portions are measured, and further, the circumferential portions are so integrated in the respective divided axial directions by using their wire diameter values as to determine the respective cross-sectional nth moments of the wire cross sections in the directions, and moreover, the maximum and minimum values of the determined cross-sectional nth moments are so compared with each other as to sort the bonding wires by the magnitudes of the moment values. In A-D having the small differences or ratios (%) of their cross-sectional second moments measured by using their second moments as their nth moments, the faultiness of their leanings are not generated, even though they have polygonal shapes wherein the differences between the measured values of their wire diameters are large. According to this method, wires having deformed cross sections, inclusive of ellipse wherein their leaning faultiness are generated can be sorted and managed, by using as a reference their cross-sectional second moment ratios (%) not larger than 1%, and this method is effective for managing the wear rates of diamond dies. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、ダイヤモンド・ダイス引き加工されたボンディングワイヤの選別方法およびボンディングワイヤ用ダイヤモンド・ダイスの管理方法で、特にボンディングワイヤの結線時のループ形成におけるリーニング不良を予測する方法およびボンディングワイヤにおける楕円ワイヤを選別する方法、並びに最終線引き加工用ダイヤモンド・ダイスにおけるベアリング部の管理方法に関する。   The present invention relates to a method for selecting a bonding wire subjected to diamond die drawing and a method for managing a diamond die for bonding wire, and more particularly, a method for predicting a leaning failure in loop formation when bonding wires are connected, and an elliptical wire in bonding wires And a method for managing bearings in a final drawing diamond die.

ボンディングワイヤは、一般的にチップとリードフレームの端子間を結線した金属線であり、半導体パッケージ内で３次元的に配線される。金属線の種類は、さまざまなものが開発されているが、基本的に純度９９．９９質量％以上のＡｕによって代表される。ボンディングワイヤにはＣｕやＰｄなどの純金属線や合金線なども用いられるが、特に貴金属線は、純度９９．９９質量％以上の高純度のＡｕ線と同様の性質を示すために代替として用いられることがある。ボンディングワイヤは一連のダイヤモンド・ダイスの引抜き加工によって一般的に線径が２５μｍの極細線まで連続伸線される。このようにして製造されたボンディングワイヤには結線後に不良が発生することがある。この不良は、主に樹脂封止時に発生し、ボンディングワイヤが樹脂とともに流れたり、蛇行したり、切断したりするのが一般的である。このようなボンディングワイヤの不良は、Ｘ線透過試験によって非破壊的に行われ、適当な画像処理プログラムを使って検出することができる。例えば、非破壊検査第５３巻第４号１９２ページの青木公也著「集積回路ボンディングワイヤの検査」によると、１９５ページの図１０にボンディングワイヤの蛇行・切断した検出例が図示されている。
しかし、近年の集積回路の集積度が向上してファインピッチ化とワイヤの細線化が同時に進行してきた。ピッチ間隔は１００μmから３５μmへと急速にファインピッチ化され、ワイヤは３０μmから１５μmへ細線化となった。この結果、リーニング不良と呼ばれる新たな不良が問題視されるようになった。
ここで、リーニング不良というのは、ボンディングワイヤの溶融ボールを半導体チップのＡｌパッドへ接合して第一ボンドを形成した後、キャピラリ−によりボンディングワイヤを繰出してループを描いた時に第一ボンドの付け根近傍で生じるボンディングワイヤの異常な傾きである（図１０参照、特開２００４−１４６７１５公報掲載図。）。このリーニング不良は隣り合うワイヤ間隔が狭まり、接近しすぎるために発生するものである。ピッチ間隔が１００μmから３５μmへと急速にファインピッチ化され、ファインピッチ化が進行するにつれてワイヤとワイヤの間隔が狭まってきた。このためワイヤとワイヤの間隔が広いときにはわずかな傾きはリーニング不良と判定されなかったのに対し、間隔が狭まってきた結果リーニング不良と判定されることが増加してきたのである。
それに対し、細線用ダイヤモンド・ダイス製造時の真円性に対する誤差は、線径が細くなっても、後述するように、減少しないが、リーニング不良はおもにワイヤ形状に起因しており、細線ではわずかな形状誤差がリーニング不良を発生させる。そのため、最終ダイヤモンド・ダイス内径の形状（ベアリング部など）の管理を徹底してリーニング不良の発生を防止することが必要になってきた。 The bonding wire is generally a metal wire that connects the terminals of the chip and the lead frame, and is three-dimensionally wired in the semiconductor package. Various types of metal wires have been developed, and are basically represented by Au having a purity of 99.99% by mass or more. For bonding wires, pure metal wires such as Cu and Pd and alloy wires are also used. In particular, noble metal wires are used as an alternative because they exhibit the same properties as high-purity Au wires with a purity of 99.99% by mass or more. May be. The bonding wire is continuously drawn to a very fine wire generally having a wire diameter of 25 μm by drawing a series of diamond dies. Defects may occur after bonding in the bonding wire manufactured in this way. This defect mainly occurs at the time of resin sealing, and the bonding wire generally flows with the resin, meanders, or cuts. Such a defective bonding wire is nondestructively performed by an X-ray transmission test, and can be detected by using an appropriate image processing program. For example, according to “Inspection of Integrated Circuit Bonding Wire” by Kimiya Aoki, Nondestructive Inspection, Vol. 53, No. 4, page 192, FIG. 10 on page 195 shows an example of detection of a meandering / cut bonding wire.
However, in recent years, the degree of integration of integrated circuits has improved, and fine pitches and thinning of wires have progressed simultaneously. The pitch interval was rapidly reduced from 100 μm to 35 μm, and the wire was thinned from 30 μm to 15 μm. As a result, a new defect called leaning defect has been regarded as a problem.
Here, the term “leaning failure” means that a bonding ball is bonded to an Al pad of a semiconductor chip to form a first bond, and then a bonding wire is drawn out by a capillary to draw a loop. This is an abnormal inclination of the bonding wire that occurs in the vicinity (see FIG. 10, published in Japanese Patent Application Laid-Open No. 2004-146715). This leaning defect occurs because the distance between adjacent wires is narrowed and too close. The pitch interval was rapidly made fine from 100 μm to 35 μm, and the wire-to-wire interval became narrower as fine pitch progressed. For this reason, when the distance between the wires is wide, a slight inclination is not determined to be a leaning failure, but as a result of the narrowing of the interval, it is increasingly determined that the leaning is defective.
On the other hand, the error with respect to roundness when manufacturing diamond dies for fine wires does not decrease as described later, even though the wire diameter is thin, but the leaning failure is mainly due to the wire shape. Shape errors cause leaning defects. For this reason, it has become necessary to thoroughly manage the shape of the inner diameter of the final diamond and die (bearing portion, etc.) to prevent the occurrence of leaning defects.

上記のリーニング不良は、ボンディングが終了した後の樹脂封止前に発生するため、結線前のボンディングワイヤを製造した直後の段階で発見することができれば、結線した半導体装置の不良が低減するため製造コストを大幅に下げることが可能になる。リーニング不良が生じる原因については、先行技術文献として前述の特開２００４−１４６７１５号公報がある。この先行技術文献では、〔０００７〕段落において、「極細線の断面形状を高い精度で測定する装置……を用いてボンディングワイヤ用極細線の断面形状を測定することにより、図１に示すループ異常はボンディング用極細線の断面形状が楕円、もしくはそれに近いゆがんだ状態の場合に起きることが見出された。」ことを開示している。   The above-mentioned leaning failure occurs before resin sealing after bonding is completed, so if it can be found immediately after manufacturing the bonding wire before connection, it will be manufactured because defects in the connected semiconductor device will be reduced. Costs can be greatly reduced. Regarding the cause of the leaning failure, there is JP-A-2004-146715 as a prior art document. In this prior art document, in the paragraph [0007], the loop anomaly shown in FIG. 1 is measured by measuring the cross-sectional shape of the bonding wire ultrafine wire using an apparatus for measuring the cross-sectional shape of the ultrafine wire with high accuracy. Has been found to occur when the cross-sectional shape of the bonding wire is elliptical or nearly distorted. "

しかし、上記先行技術が対策として掲げた「引き抜き加工後のボンディング用極細線の線方向に対して直角となる断面の、最大直径と最小直径の差が線径の３％を越えるものを不良品とする」やり方は、ダイヤモンド・ダイスの寿命を管理する上では有効であるものの、第一ボンドの形成時に生じるリーニング不良に対しては必ずしも有効ではない。確かに、極細線をダイヤモンド・ダイスによって連続的に引抜き加工していくと、ダイヤモンド・ダイス孔が磨耗していきダイヤモンド・ダイス孔が大きくなり、このときダイヤモンド・ダイス孔の磨耗は場合によってはダイヤモンド・ダイス孔の円周上に不均一に発生する。そのため極細線の線径の最大直径と最小直径の差も次第に大きくなり、やがて線径の３％を越えるようになってしまうこともある。
しかし、このように断面形状における最大直径と最小直径の差はダイヤモンド・ダイスの磨耗に伴なって発生するものであるから、最大直径と最小直径の差が線径の３％を越えるまでダイヤモンド・ダイスを使い続ける前に、ワイヤの（平均）線径が許容度を越えて変化してしまう。
これに対して、ボンディングワイヤの（平均）線径はより厳密に管理される必要があり、ダイヤモンド・ダイスの寿命管理上、一般にダイヤモンド・ダイスでは最大直径と最小直径の差が線径の２％を越えることは希である。
一方、最大直径と最小直径の差が線径の１％以下でもリーニング不良は発生することがあり、逆に線径の３％以上あってもリーニング不良が発生しないボンディングワイヤがあった。
このことは、これらの差が１％を越えてもリーニング不良とならないものがあるにもかかわらず、品質管理上、１％よりも許容閾値を低くしなければならないことを意味し、他方でリーニング不良が発生しないボンディングワイヤを廃棄するなど、著しいロスを生じることともなった。
そもそも、最大直径と最小直径の差は、ワイヤの全円周形状の一部分に対する計測値であるから、ワイヤ全体の性状を示す測定値ではなく、場合によっては測定誤差と区別するのも難しい。したがって、最大直径と最小直径の差からワイヤ全体の性状を求めることは現実的でなく、精度が極端に低くなる。このように先行技術に示されたこれまでのやり方ではリーニング不良を解消することができず、その結果最終線引き加工用ダイヤモンド・ダイスにおけるベアリング部を管理することもできなかった。また、ワイヤの全円周形状のうち最大直径と最小直径の差だけでは、後述するように楕円ワイヤと多角形ワイヤとを選別することができなかった。
特開２００４−１４６７１５号公報 「非破壊検査」第５３巻第４号掲載論文、「集積回路ボンディングワイヤの検査」青木公也、１９５ページの図１０ However, the above-mentioned prior art proposed as a countermeasure “If the difference between the maximum diameter and the minimum diameter of the cross section perpendicular to the wire direction of the fine wire for bonding after drawing is over 3% of the wire diameter, it will be defective. The “to do” method is effective in managing the life of the diamond die, but is not necessarily effective for the leaning failure that occurs during the formation of the first bond. Certainly, when the ultrafine wire is continuously drawn with a diamond die, the diamond die hole wears and the diamond die hole becomes larger.・ It occurs unevenly on the circumference of the die hole. For this reason, the difference between the maximum diameter and the minimum diameter of the ultrafine wire gradually increases and may eventually exceed 3% of the wire diameter.
However, since the difference between the maximum diameter and the minimum diameter in the cross-sectional shape is caused by the wear of the diamond die, the diamond diameter is increased until the difference between the maximum diameter and the minimum diameter exceeds 3% of the wire diameter. Before continuing to use the dice, the (average) wire diameter of the wire changes beyond tolerance.
On the other hand, the (average) wire diameter of the bonding wire needs to be managed more strictly. For the diamond die life management, the difference between the maximum diameter and the minimum diameter is generally 2% of the wire diameter. It is rare to exceed.
On the other hand, even when the difference between the maximum diameter and the minimum diameter is 1% or less of the wire diameter, a leaning defect may occur.
This means that even if these differences exceed 1%, there is no leaning failure, but for quality control, the tolerance threshold must be lower than 1%. It also caused a significant loss, such as discarding bonding wires that do not cause defects.
In the first place, since the difference between the maximum diameter and the minimum diameter is a measurement value for a part of the entire circumferential shape of the wire, it is not a measurement value indicating the properties of the entire wire, and in some cases it is difficult to distinguish from a measurement error. Therefore, it is not practical to obtain the properties of the entire wire from the difference between the maximum diameter and the minimum diameter, and the accuracy becomes extremely low. Thus, the conventional method shown in the prior art cannot solve the leaning failure, and as a result, the bearing portion in the final drawing diamond die cannot be managed. In addition, the elliptical wire and the polygonal wire cannot be selected only by the difference between the maximum diameter and the minimum diameter among the entire circumferential shapes of the wires, as will be described later.
JP 2004-146715 A "Non-destructive inspection", Volume 53, No. 4 paper, "Inspection of integrated circuit bonding wires" Kimiya Aoki, page 195, Fig. 10

本発明は、基本的に上記のリーニング不良をボンディング工程で発生させないためになされたものである。すなわち、本発明は、これまでボンディングワイヤの結線時のループ形成においてリーニング不良がなぜ生じるのか明らかでなかった原因を解明することによってなされたものである。本発明者らはこの解明過程で、楕円を含む歪んだ形状の異形断面ワイヤはワイヤ最大直径と最小直径の差またはワイヤ最大直径と最小直径の差をワイヤ線径で除した値が断面二次モーメント比と比例関係にあることを見いだし、多角形ワイヤには比例関係が無いことを確認した。ワイヤ最大直径と最小直径の差と断面Ｎ次モーメント比を利用することにより、これまで楕円ワイヤと多角形ワイヤとを分類分けし、識別することができなかった課題の解決に成功した。また、本発明者らはリーニング不良の原因がボンディングワイヤの断面形状と関連することを解明し、結線前の段階でボンディングワイヤを選別することによってリーニング不良の解決に成功した。また、リーニング不良がボンディングワイヤを介して最終ダイヤモンド・ダイスのベアリング部の形状と関連していることがわかったので、最終線引きダイヤモンド・ダイスを管理することによってリーニング不良を解決する方法を解明した。   The present invention is basically made in order to prevent the above-mentioned leaning defect from occurring in the bonding process. That is, the present invention has been made by elucidating the cause that has not been clarified why the leaning failure has occurred in the loop formation when bonding wires are connected. In this elucidation process, the present inventors have found that a deformed cross-section wire including an ellipse is obtained by dividing the difference between the maximum wire diameter and the minimum wire diameter or the difference between the wire maximum diameter and the minimum wire diameter by the wire diameter. It was found that there was a proportional relationship with the moment ratio, and it was confirmed that the polygonal wire had no proportional relationship. By using the difference between the maximum diameter and the minimum diameter of the wire and the N-th moment ratio of the cross section, the elliptical wires and the polygonal wires were classified and succeeded in solving the problems that could not be identified. In addition, the present inventors have clarified that the cause of the leaning failure is related to the cross-sectional shape of the bonding wire, and succeeded in solving the leaning failure by selecting the bonding wire before connection. Also, since it was found that the leaning defect was related to the shape of the bearing part of the final diamond die through the bonding wire, the method for solving the leaning defect by managing the final drawing diamond die was clarified.

上記の課題を解決するための、本発明のボンディング前に予測する選別方法は、以下の通りである。
（ａ） 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおけるリーニング不良の選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、
３） その求められた断面Ｎ次モーメントの最大値と最小値とを比較する工程によって、
ボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。
（ｂ） 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおける異形断面ワイヤ楕円ワイヤの選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２）その線径を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における軸方向断面Ｎ次モーメントの最大値と最小値を求める工程、
４） その求められた線径の最大値と最小値との差をＸ座標としその断面Ｎ次モーメントの最大値と最小値との差をＹ座標としてプロットして比較する工程によって、
ボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。
（ｃ）半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、
３） その求められた断面Ｎ次モーメントの最大値と最小値とを比較する工程によって、
ボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の適否を判定する管理方法。
（ｄ）半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における断面Ｎ次モーメントの最大値と最小値を求める工程、
４） その線径の最大値と最小値との差およびその断面Ｎ次モーメントの最大値と最小値との差を求める工程、
５）その求められた線径の最大値と最小値との差をＸ座標としその断面Ｎ次モー メントの最大値と最小値との差をＹ座標としてプロットして比較する工程によ って、
ボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の適否を判定する管理方法。 In order to solve the above-described problems, the screening method predicted before bonding according to the present invention is as follows.
(A) A method for selecting a leaning defect in a bonding wire that three-dimensionally connects between a semiconductor chip and a terminal such as a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) A step of integrating for each divided axial direction of the circumferential portion using the wire diameter to obtain a cross-sectional Nth moment in the direction;
3) By comparing the maximum value and the minimum value of the obtained sectional N-th moment,
A bonding wire selection method for determining a leaning defect in loop formation when bonding wires are connected.
(B) A method for selecting a deformed cross-section wire elliptical wire in a bonding wire for connecting three-dimensionally between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) Step of integrating for each divided axial direction of the circumferential portion using the wire diameter to obtain a cross-sectional Nth moment in the direction;
3) A step of obtaining a maximum value and a minimum value of the wire diameter in the circumferential portion, and a maximum value and a minimum value of the axial sectional N-th moment in the circumferential portion from the measured values,
4) By plotting and comparing the difference between the maximum value and the minimum value of the obtained wire diameter as the X coordinate and the difference between the maximum value and the minimum value of the cross-sectional Nth moment as the Y coordinate,
A bonding wire selection method for determining a leaning defect in loop formation when bonding wires are connected.
(C) A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) A step of integrating each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional Nth moment in the direction,
3) By comparing the maximum value and the minimum value of the obtained sectional N-th moment,
A management method for determining the suitability of a bearing part in a diamond die for final drawing of a bonding wire.
(D) A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) A step of integrating each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional Nth moment in the direction,
3) A step of obtaining a maximum value and a minimum value of the wire diameter in the circumferential portion from the measured values, and a maximum value and a minimum value of the cross-sectional N-th moment in the circumferential portion,
4) A step of obtaining a difference between the maximum value and the minimum value of the wire diameter and a difference between the maximum value and the minimum value of the cross-sectional Nth moment,
5) By the process of plotting and comparing the difference between the maximum value and minimum value of the obtained wire diameter as the X coordinate and the difference between the maximum value and minimum value of the cross sectional Nth moment as the Y coordinate. ,
A management method for determining the suitability of a bearing part in a diamond die for final drawing of a bonding wire.

また、さらに具体的な要件は、以下の通りである。
(ｆ) 前記の断面Ｎ次モーメントの最大値と最小値との比較を、最大値と最小値との差を最大値または最小値で除したときの断面２次モーメント比で評価することを特徴とする上記（ａ）または（ｂ）に記載のボンディングワイヤの良否を予測するボンディングワイヤの選別方法。
（ｇ） 前記の断面Ｎ次モーメントの最大値と最小値との比較を、最大値と最小値との差を最大値または最小値で除したときの断面２次モーメント比で評価することを特徴とする上記（c）または（d）のボンディングワイヤ用ダイヤモンド・ダイスの管理方法。 Further specific requirements are as follows.
(f) The comparison between the maximum value and the minimum value of the cross-sectional N-th moment is evaluated by the cross-sectional second moment ratio when the difference between the maximum value and the minimum value is divided by the maximum value or the minimum value. The bonding wire selection method for predicting the quality of the bonding wire according to (a) or (b).
(G) The comparison between the maximum value and the minimum value of the cross-sectional N-th moment is evaluated by the cross-sectional second moment ratio obtained by dividing the difference between the maximum value and the minimum value by the maximum value or the minimum value. (C) or (d) the method for managing diamond dies for bonding wires.

まずリーニング不良と本発明との関連について説明する。ボンディングワイヤの先端に溶融ボールをつくり半導体チップ上へボンディングして第一ボンドを形成した場合、ボンディングワイヤの先端部分は引抜き加工による塑性ひずみは開放されているが、熱影響を受けていない部分は塑性ひずみがそのまま残っている。この熱影響を受けた部分と受けない部分との境界は機械的強度が弱い箇所であり、曲がりやすい箇所となるが、第一ボンドを形成した後にキャピラリ−が上昇運動をしている間はボンディングワイヤに大きな曲げ応力がかからないので、ボンディングワイヤはすべてほぼ鉛直に立っている。しかし、キャピラリ−を第一ボンドから第二ボンド方向に移動してワイヤにループを描きはじめさせた途端に、ボンディングワイヤに曲げ応力が加わりこの曲げ応力が上記の熱影響の境界部へ集中して境界部が屈曲する。本発明者らはこの現象を高速度カメラによって確認した。換言すると、キャピラリ−によって第一ボンドから第二ボンド方向へループを描く際に、ボンディングワイヤは拘束されてボンディングワイヤには第一ボンドから第二ボンド方向の応力が加わる。ボンディングワイヤの第一ボンドの付け根部分からやや上部には熱影響の境界部分があり、その部分に強い曲げ応力が加わる。ループは第一ボンドからキャピラリ−によって大きく曲げられる箇所まで進むあいだに線材のもっとも弱い箇所へいちじるしく過度の力が加わるタイミングで屈曲する。このワイヤの屈曲が、キャピラリ−の軌跡とは異なる方向に曲がること、すなわち、ばらつくことがリーニング不良の主な現象であると思われる。   First, the relationship between the leaning failure and the present invention will be described. When a molten ball is made at the tip of the bonding wire and bonded to the semiconductor chip to form the first bond, the tip of the bonding wire is free from plastic strain due to drawing, but the portion not affected by heat Plastic strain remains as it is. The boundary between the part that is affected by heat and the part that is not affected is a part where the mechanical strength is weak and easy to bend. However, while the capillary is moving upward after the first bond is formed, bonding is performed. Since no great bending stress is applied to the wires, all the bonding wires are almost vertical. However, as soon as the capillary is moved from the first bond to the second bond and the wire begins to draw a loop, a bending stress is applied to the bonding wire, and this bending stress is concentrated at the boundary of the thermal effect described above. The bend is bent. The present inventors confirmed this phenomenon with a high-speed camera. In other words, when the loop is drawn from the first bond to the second bond by the capillary, the bonding wire is restrained, and stress in the first bond to the second bond direction is applied to the bonding wire. There is a boundary part of the heat effect slightly above the base part of the first bond of the bonding wire, and a strong bending stress is applied to this part. The loop bends at the timing when a remarkably excessive force is applied to the weakest part of the wire while proceeding from the first bond to the part that is largely bent by the capillary. It seems that the main phenomenon of the leaning failure is that the bending of the wire bends in a direction different from the capillary trajectory.

本発明者らは、キャピラリ−の軌跡とは異なる方向に曲がる（ばらつく）要因が円周方向のワイヤ形状の不均一さによる断面Ｎ次モーメントに起因していることを突き止めた。すなわち、ワイヤ断面形状の円周全体の性状を断面Ｎ次モーメントで表すことによって、これらの機械的特性に影響を与えるワイヤ形状の不均一さを評価することに成功した。以下、断面Ｎ次モーメントを代表的な断面二次モーメントで説明する。
線材を一般的に曲げ加工する場合、曲がりやすさや曲がりにくさは線材の形状に起因する物理特性からきている。最終ダイヤモンド・ダイスの引抜き加工によって製造された線径が２５μｍ以下の極細線の場合、ダイヤモンド・ダイスにおけるベアリング部は最大直径と最小直径の差がこれまでは通常１％未満なので真円として取り扱っていたが、本発明者らはその真円部分を更に拡大して多数の大小の円弧曲線によって構成されているものと把握することにした。断面形状をこのような大小の円弧曲線によって評価すると、これまで真円部分と考えられていたものが２種類に分類することができた。一つは楕円形状のもの（ただし、最大直径と最小直径の差は通常１％未満である。）、他方は多角形形状のもの（ただし、最大直径と最小直径の差は通常１％未満である。）である。そして、楕円形状のものがリーニング不良を起こし、多角形のものがぎらぎら光る乱反射を生じる原因であることがわかった。この楕円形状のものと多角形形状のものとを区別するのに断面２次モーメントが有効であることがわかった。
本発明者らは楕円形状のボンディングワイヤを多数本ボンディングしてさらに詳しく調べたところ、キャピラリ−によってボンディングワイヤに横方向の応力が加わった場合、ボンディングワイヤの第一ボンドを中心点とした鉛直方向からの傾きが正規分布を描くことがわかった。この正規分布は楕円傾向が強まるとともに幅が広がる傾向にあることがわかった。正規分布の幅が広がることは、ボンディングワイヤの傾きが大きくなることを示し、傾きが一定値以上のものがリーニング不良となる。
本発明者らはリーニングの程度をボンディングワイヤの断面形状に由来する断面２次モーメントによって表すことができると考えた。よって、接合前にボンディングワイヤの断面を多数の方向に分割してそれぞれの方向における断面２次モーメントを精密に測定しておけば、曲がりにくさの度合いを予測することができる。そこで、本発明者らはボンディングワイヤの断面２次モーメントを、同一円周上で複数方向測定することによってそれらの測定値から断面２次モーメントの最大値と最小値を求め、それを比較する工程によって、ボンディングワイヤの第一ボンド後におけるリーニング不良の良否を予測することに成功したものである。第一ボンドされたワイヤの傾きは正規分布として表れる。リーニング不良の良否と断面２次モーメントの最大値と最小値との比較は最大値または最小値で除した比で比較することが好ましい。なお、ボンディングワイヤの長手方向の断面２次モーメントは、高純度のＡｕ等の変形しやすい極細線をダイヤモンド・ダイスによって引抜き加工しているので、最終ダイヤモンド・ダイスにおけるベアリング部の形状が反映され、極細線の長手方向はほぼ同一の傾向を示すとして取り扱って差し支えない。
なお、断面２次モーメントは線材の曲げ応力に対して関連する物性値であるが、断面１次モーメントでも断面３次モーメントでも、力学的なモーメントとして扱う上で断面2次モーメントと同様な傾向を示すものと考えられる。 The present inventors have found that the factor of bending (variation) in a direction different from the capillary trajectory is caused by the N-th moment of the cross section due to the non-uniformity of the wire shape in the circumferential direction. That is, by expressing the overall shape of the wire cross-sectional shape by the N-th moment of the cross-section, we succeeded in evaluating the non-uniformity of the wire shape that affects these mechanical characteristics. Hereinafter, the cross-sectional Nth moment will be described as a typical cross-sectional second moment.
When a wire is generally bent, the ease of bending and the difficulty of bending come from the physical characteristics resulting from the shape of the wire. In the case of extra fine wires with a diameter of 25 μm or less manufactured by drawing the final diamond dies, the difference between the maximum diameter and the minimum diameter of diamond dies is usually less than 1% so far, and is treated as a perfect circle. However, the inventors of the present invention have further enlarged the true circle portion and grasped that it is constituted by a large number of large and small arc curves. When the cross-sectional shape was evaluated by such a large and small arc curve, what was considered to be a perfect circle part until now could be classified into two types. One is oval (however, the difference between the maximum and minimum diameters is usually less than 1%), and the other is polygonal (but the difference between the maximum and minimum diameters is usually less than 1%) Yes.) Then, it was found that the elliptical shape causes the leaning failure, and the polygonal shape causes the irregular reflection that glitters. It was found that the second moment of section is effective in distinguishing between the elliptical shape and the polygonal shape.
The inventors of the present invention conducted a detailed examination by bonding a large number of elliptical bonding wires. When lateral stress is applied to the bonding wire by the capillary, the vertical direction with the first bond of the bonding wire as the center point It was found that the slope from drew a normal distribution. It was found that this normal distribution tends to increase in width as the elliptical tendency increases. An increase in the width of the normal distribution indicates that the inclination of the bonding wire is increased, and a thing with an inclination of a certain value or more becomes a leaning defect.
The present inventors considered that the degree of leaning can be expressed by the second moment of section derived from the sectional shape of the bonding wire. Therefore, the degree of difficulty in bending can be predicted by dividing the cross section of the bonding wire into a large number of directions and accurately measuring the secondary moment in each direction before joining. Therefore, the present inventors measure the cross-sectional secondary moment of the bonding wire in a plurality of directions on the same circumference to obtain the maximum value and the minimum value of the cross-sectional secondary moment from the measured values, and compare them. Thus, the success or failure of the leaning defect after the first bonding of the bonding wire was successfully predicted. The slope of the first bonded wire appears as a normal distribution. The comparison between the quality of the leaning failure and the maximum value and the minimum value of the cross-sectional secondary moment is preferably made by a ratio divided by the maximum value or the minimum value. In addition, the cross-sectional secondary moment in the longitudinal direction of the bonding wire reflects the shape of the bearing part in the final diamond die because the ultrafine wire that is easily deformed, such as high-purity Au, is drawn with a diamond die. The longitudinal direction of the ultrafine wire may be handled as indicating almost the same tendency.
Note that the secondary moment of section is a physical property value related to the bending stress of the wire, but the same moment as that of the sectional secondary moment is treated in both the first moment and the third moment as a mechanical moment. It is thought to show.

つぎに、リーニング不良の原因となる楕円ワイヤとそうではない多角形ワイヤの種分け方法について説明する。
前述の先行技術における楕円ワイヤの選別法においては、ワイヤ線形の最大値と最小値とを比較するものであったが、レーザー回折による測定値は測定箇所のワイヤ径を回折像から測定するものであって、断面形状を表わすものではないから、これらの差は楕円に該当する場合もあれば、多角形の陵と辺との差を表わす場合もある。
本発明者らは、リーニング不良の原因を断面形状の不均一さ、すなわち楕円を含むゆがんだ断面形状に起因する機械的特性の異方性にあると考え、断面形状で多角形状のものがこのような機械的特性の異方性がなく、リーニング不良を発生しないことから、これらの多角形ワイヤを楕円を含むゆがんだ断面形状、いわゆる異形断面のワイヤと区別する方法として、断面Ｎ次モーメントによる評価法が有効であることを突き止めたのである。
多角形ワイヤの変形の度合いが大きくなると、ギラと呼ばれる外観不良になることがある。ギラは、極細線からの乱反射によってぎらぎら光るワイヤのことを意味する。この現象はボンディングワイヤへ入射した光が反射される時にワイヤ表面が一様でないために発生するものである。つまり、ワイヤ断面が完全な円ではなく多角形によることに起因する。しかし、これまでは楕円ワイヤと多角形ワイヤを完全に種分けする方法は見つかっていなかった。本発明者らは、断面２次モーメントの最大値と最小値の差を最大値または最小値で除した比と、線径の最大値と最小値の差または線径の最大値と最小値を線径で除した値を比較することによって楕円ワイヤと多角形ワイヤを識別し、楕円ワイヤを定量化することに成功した。
なお、ここでも断面１次モーメントでも断面３次モーメントでも、断面形状の起因する機械的特性の異方性を評価するうえで断面２次モーメントと同様な傾向を示すものと考えられる。 Next, a method of classifying an elliptical wire that causes a leaning failure and a polygonal wire that does not cause the failure will be described.
In the above-described prior art method for selecting an elliptical wire, the maximum value and the minimum value of the wire alignment are compared, but the measured value by laser diffraction is to measure the wire diameter at the measurement location from the diffraction image. In addition, since it does not represent a cross-sectional shape, these differences may correspond to ellipses or may represent differences between polygonal ridges and sides.
The present inventors consider that the cause of the leaning failure is the non-uniformity of the cross-sectional shape, that is, the anisotropy of the mechanical properties due to the distorted cross-sectional shape including the ellipse, and the polygonal cross-sectional shape is this Since there is no anisotropy of mechanical properties and no leaning failure occurs, a method of distinguishing these polygonal wires from a distorted cross-sectional shape including an ellipse, that is, a so-called deformed cross-sectional wire is based on the N-order moment They found that the evaluation method was effective.
When the degree of deformation of the polygonal wire is increased, an appearance defect called “glare” may occur. Gira refers to a wire that glitters due to irregular reflection from a fine wire. This phenomenon occurs because the surface of the wire is not uniform when the light incident on the bonding wire is reflected. That is, the wire cross section is not a perfect circle but a polygon. However, until now, no method has been found for completely classifying elliptical wires and polygonal wires. The present inventors calculated the ratio obtained by dividing the difference between the maximum value and minimum value of the secondary moment of section by the maximum value or minimum value, the difference between the maximum value and minimum value of the wire diameter, or the maximum value and minimum value of the wire diameter. By comparing the value divided by the wire diameter, we identified the elliptical wire and the polygonal wire, and succeeded in quantifying the elliptical wire.
In this case, it is considered that the same moment as that of the cross-sectional secondary moment is exhibited in evaluating the anisotropy of the mechanical characteristics caused by the cross-sectional shape, either in the cross-sectional primary moment or in the cross-sectional third moment.

本発明の効果は、結線前の段階でボンディングワイヤを選別することによってリーニング不良が解決できるようになったことである。さらに、楕円ワイヤを定量化することによってリーニング不良が解決できるようになったことである。また、ボンディングワイヤの表面形状は最終ダイヤモンド・ダイスのベアリング部の形状と関連しているので、最終線引きダイヤモンド・ダイスを管理することによって結果的にリーニング不良が解決できた。   The effect of the present invention is that the leaning failure can be solved by selecting the bonding wires before the connection. Furthermore, the leaning failure can be solved by quantifying the elliptical wire. In addition, since the surface shape of the bonding wire is related to the shape of the bearing portion of the final diamond die, the final drawing diamond die was managed, and as a result, the leaning failure could be solved.

本発明においてボンディングワイヤに利用される金属線は、純度９９．９９質量％以上のＡｕ線が好ましい。高純度で柔らかいため引抜き加工されるダイヤモンド・ダイスのベアリング部の形状がそのままボンディングワイヤの外形に反映されるからである。同様の理由から高純度のＣｕや軟質の貴金属合金、例えばＡｕ−１５質量％Ａｇ合金、Ａｕ−１質量％Ｐｄ合金またはこれらの金属や合金にＣａ、Ｂｅ、Ｉｎ、Ｓｎ、希土類元素などの微量添加元素を含有させたものなどを用いることができる。   In the present invention, the metal wire used for the bonding wire is preferably an Au wire having a purity of 99.99% by mass or more. This is because the shape of the bearing portion of the diamond die that is drawn is reflected in the outer shape of the bonding wire as it is because it is high purity and soft. For the same reason, high-purity Cu and soft noble metal alloys such as Au-15 mass% Ag alloy, Au-1 mass% Pd alloy, or trace amounts of Ca, Be, In, Sn, rare earth elements and the like in these metals and alloys. A material containing an additive element or the like can be used.

本発明のボンディングワイヤの線径は３０μｍ以下であれば特に制限はないが、１０〜２５μｍの範囲が好ましい。リーニング不良はファインピッチ領域で発生する不良であり、一般的には細線が用いられるからである。   The wire diameter of the bonding wire of the present invention is not particularly limited as long as it is 30 μm or less, but a range of 10 to 25 μm is preferable. This is because a leaning defect is a defect that occurs in a fine pitch region, and thin lines are generally used.

純度９９．９９９質量％以上の高純度金へ微量元素を所定量含有させて純度９９．９９質量％以上の高純度金を調製した。この調製品を真空溶解炉で溶解鋳造し、伸線加工した。そして、最終線径２３μｍのところで、孔形状を異ならせた６種類のダイヤモンド・ダイス（公称径はいずれも２３μｍである。）を用意して６種類の極細線を作成し、それぞれ最終熱処理した。この６種類のワイヤの外径をレーザ回折を利用した線径測定器によって各々測定した。このような線径測定器としては、株式会社キーエンス製のデジタル寸法測定器（LS-7000）や東京光電子工業株式会社製のレーザマイクロゲージ D5やCERSA社製のLDSN-200等を利用できる。
６種類のワイヤ径の測定結果を図１のプロットＡ〜Ｆに示す。また、ワイヤ断面の半
径方向を拡大した断面形状を図２のＡ〜Ｆに示す。図１のプロットＡ〜Ｆは、図２のプロットＡ〜Ｆに対応する。ここで、Ｏｖａｌｉｔｙとは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」をいい、１００×（（ボンディングワイヤの線径の最大値）−（ボンディングワイヤの線径の最小値））／（ボンディングワイヤの線径）と定義し、「断面２次モーメント比（％）」は、ボンディングワイヤの断面2次モーメントを半周１８０度に対して１１．２５度ステップで１６箇所測定した中で最大値と最小値を求め、１００×（最大値−最小値）／（最大値）によって定義した。
断面二次（N次）モーメントは次のようにして得られる。
ワイヤ断面を図３の半円に示すように１１．２５度ステップで１６の円周部分に等分割
して、それぞれの円周部分ごとに直径を測定し、半径ｒを求める。
測定された半径ｒから図４に示すように各円周部分の半径ｒに対応する、Ｘ軸に対する高さｙ、及びＸ軸に投影した幅がそれぞれ、ｒsinθ及びr cosθから得られる。
具体的には、高さｙは分割された円周部分の中間で測定された測定値、或いはその円周範囲での平均値などで近似し、幅ｘはこれら円周部分の前後で測定されたｒcosθ値間で引算するなどして得られるが、幾何学上の手法であるから略す。
このようにして得られた各円周部分毎のｘ、ｙ値から長方形に近似した断面形状を表わすと、図５のようになる。このようにして近似した断面に対する断面Ｎ次モーメントを積分して求めることが出来る。以下、同様にして順次分割数１６に対応して１１．２５度ずつずらしてそれぞれの方向毎の半円の断面Ｎ次モーメントを求めることが出来る。
これらの分割数は１６に限るものではないが、分割間隔を大きくすると断面形状を正確に反映できないので、概ね１６以上に分割して計測することが好ましい。
また、図２の濃い実線と薄い実線は、ワイヤ断面の半円形状を示し、同じワイヤの測定位置をワイヤの長手方向に10ｍずらして変化させ２回測定した結果である。また、下中央部の四角はワイヤ断面の中心点である。
図１のＡ〜Ｆの６種類のワイヤ径の測定結果と、ワイヤ断面の半径方向を拡大した図２のＡ〜Ｆの断面形状を参照しながら比較すると、（１）図１のＡプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面２次モーメント比（％）」はいずれも低い値であり、図２−Ａから真円に近い形状である。（２）図１−Ｃ、Ｆプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面２次モーメント比（％）」はいずれも増加しており、図２−Ｃ、Ｆから楕円に近い形状であることが確認できる。（３）一方、図１―Ｂ、Ｄ、Ｅプロットは、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」が増加しても、「断面２次モーメント比（％）」の増加は小さく、図２−Ｂ、Ｄ、Ｅから多角形に近い形状である。
したがって、（１）〜（３）のプロットの関係から、「断面２次モーメント」又は「断面２次モーメント比（％）」の大小によって、楕円ワイヤと多角形ワイヤとを識別することができる。 A predetermined amount of a trace element was contained in high-purity gold having a purity of 99.999% by mass or more to prepare high-purity gold having a purity of 99.99% by mass or more. This preparation was melt cast in a vacuum melting furnace and drawn. Then, at the final wire diameter of 23 μm, six types of diamond dies having different hole shapes (the nominal diameter is 23 μm) were prepared to prepare six types of ultrafine wires, and each was subjected to final heat treatment. The outer diameters of these six types of wires were measured with a wire diameter measuring device using laser diffraction. As such a wire diameter measuring device, a digital dimension measuring device (LS-7000) manufactured by Keyence Corporation, a laser micro gauge D5 manufactured by Tokyo Koden Kogyo Co., Ltd., LDSN-200 manufactured by CERSA, or the like can be used.
The measurement results of the six types of wire diameters are shown in plots A to F in FIG. Moreover, the cross-sectional shape which expanded the radial direction of the wire cross section is shown to AF of FIG. The plots A to F in FIG. 1 correspond to the plots A to F in FIG. Here, “Ovality” means “value obtained by dividing the difference between the maximum wire diameter and the minimum diameter by the wire diameter (%)”, and 100 × ((maximum value of the wire diameter of the bonding wire) − (the wire diameter of the bonding wire). ) / (Bonding wire diameter), and the “secondary moment ratio of cross section (%)” is 16 in steps of 11.25 degrees with respect to the second moment of bonding section of 180 degrees per half circumference. The maximum value and the minimum value were obtained among the points measured and defined by 100 × (maximum value−minimum value) / (maximum value).
The cross-sectional secondary (Nth) moment is obtained as follows.
As shown in the semicircle of FIG. 3, the wire cross section is equally divided into 16 circumferential portions in 11.25 degree steps, the diameter is measured for each circumferential portion, and the radius r is obtained.
From the measured radius r, as shown in FIG. 4, the height y with respect to the X axis and the width projected on the X axis corresponding to the radius r of each circumferential portion are obtained from r sin θ and r cos θ, respectively.
Specifically, the height y is approximated by a measured value measured in the middle of the divided circumferential portions, or an average value in the circumferential range, and the width x is measured before and after these circumferential portions. Although it is obtained by subtracting between the rcos θ values, it is omitted because it is a geometrical method.
FIG. 5 shows a cross-sectional shape approximated to a rectangle from the x and y values for each circumferential portion thus obtained. It can be obtained by integrating the cross-sectional Nth moment with respect to the cross section approximated in this way. In the same manner, the N-th moment of the semicircular cross section in each direction can be obtained by sequentially shifting by 11.25 degrees corresponding to the division number of 16.
The number of divisions is not limited to 16, but if the division interval is increased, the cross-sectional shape cannot be accurately reflected. Therefore, it is preferable to divide the measurement into approximately 16 or more.
Also, the dark solid line and the thin solid line in FIG. 2 indicate the semicircular shape of the wire cross section, and are the results of measuring twice by changing the measurement position of the same wire by shifting by 10 m in the longitudinal direction of the wire. The square at the lower center is the center point of the wire cross section.
When comparing the measurement results of the six types of wire diameters A to F in FIG. 1 with reference to the cross-sectional shapes of A to F in FIG. 2 in which the radial direction of the wire cross section is enlarged, (1) A plot in FIG. “Value obtained by dividing difference between wire maximum diameter and minimum diameter by wire diameter (%)” and “cross section secondary moment ratio (%)” are both low values, and a shape close to a perfect circle from FIG. It is. (2) Figures 1-C and F plots show that both "value (%) obtained by dividing difference between wire maximum diameter and minimum diameter by wire wire diameter (%)" and "section moment ratio (%)" are increasing. 2-C and F, it can be confirmed that the shape is close to an ellipse. (3) On the other hand, the plots of FIGS. 1-B, D, and E show that even if the “value (%) obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter” increases, %) ”Is small, which is a shape close to a polygon from FIGS.
Therefore, the elliptical wire and the polygonal wire can be identified from the relationship of the plots of (1) to (3) depending on the magnitude of the “secondary moment of section” or “ratio of second moment of section (%)”.

実施例１と同様にして、最終線径２５μｍの６種類のダイヤモンド・ダイス（公称径はいずれも２５μｍである。）を使用して６種類の極細線を作成し、それぞれ最終熱処理した。
６種類のワイヤ径の測定結果を図６のプロットＧ〜Ｌに示す。また、ワイヤ断面の半径方向を拡大した断面形状を図７のＧ〜Ｌに示す。図６のプロットＧ〜Ｌは図７のＧ〜Ｌと対応する。ここで、断面形状における図７の濃い実線は測定値のワイヤ直径から推定したワイヤ断面の半円形状、薄い実線はワイヤが完全な真円と仮定した場合のワイヤ断面の半円形状を示す。また、下中央部の四角はワイヤ断面の中心点である。
図６のＧ〜Ｌのプロットとその断面形状を表わす図７のプロットＧ〜Ｌの比較から明らかなとおり、ワイヤ形状が楕円形のＫ、Ｌは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面２次モーメント比（％）」とで相関がみられるが、ワイヤ形状が多角形のＨ、Ｉ、Ｊは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」が増加しても「断面２次モーメント比（％）」は低く、これらの間に相関関係が無いことがわかる。
したがって、実施例1と実施例２の結果から、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面２次モーメント比（％）」との相関関係により楕円ワイヤと多角形ワイヤとを識別することができ、線径の測定値間の差には特に依存しないことが確認できる。 In the same manner as in Example 1, six types of ultrafine wires were prepared using six types of diamond dies having a final wire diameter of 25 μm (both nominal diameters are 25 μm), and each was subjected to final heat treatment.
The measurement results of the six types of wire diameters are shown in plots GL in FIG. Moreover, the cross-sectional shape which expanded the radial direction of the wire cross section is shown to GL of FIG. Plots G to L in FIG. 6 correspond to G to L in FIG. Here, the dark solid line in FIG. 7 in the cross-sectional shape indicates the semicircular shape of the wire cross section estimated from the measured wire diameter, and the thin solid line indicates the semicircular shape of the wire cross section when the wire is assumed to be a perfect circle. The square at the lower center is the center point of the wire cross section.
As apparent from the comparison of the plots G to L in FIG. 6 and the plots G to L in FIG. 7 showing the cross-sectional shape, K and L in which the wire shape is an ellipse are “the difference between the maximum diameter and the minimum diameter of the wire There is a correlation between the value divided by the diameter (%) and the cross-sectional second moment ratio (%), but the H, I, and J of the polygonal wire shape indicate the difference between the maximum wire diameter and the minimum diameter. Even if the value (%) divided by the wire diameter is increased, the “secondary moment ratio (%)” is low and it can be seen that there is no correlation between them.
Therefore, from the results of Example 1 and Example 2, the correlation between “the value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)” and the “second moment ratio (%)” is obtained. An elliptical wire and a polygonal wire can be distinguished, and it can be confirmed that there is no particular dependence on the difference between the measured values of the wire diameter.

次に、実施例２の６種類のワイヤを用い、株式会社新川製のワイヤボンダ（ＵＴＣ−４００型）を使って、大気中、０．５ミリ秒の放電時間にて溶融ボール（ボール径３８μｍ）を作成し、１００μｍ角の純Ａｌパッド上へ圧着径４５μｍで所定のループ条件（高さ３００μｍ、長さ４ｍｍ）にて１０，０００回ボンディングしたところ、図１０に示すようなリーニング不良が発生していた。このリーニング不良（本数）の結果を「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面2次モーメント比（％）」との相関で図８、図９に示す。図８によれば、「リーニング不良（本数）」と「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」との相関係数は０．６４と低いのに対し、図９の「リーニング不良（本数）」と「断面２次モーメント比（％）」との相関係数は０．９７と高く、ほぼ直線上に分布していることがわかる。
したがって、リーニング不良が発生するのは楕円形状のワイヤに限定され、楕円形状のワイヤを識別するには「断面２次モーメント比（％）」が必須条件となっている。つまり、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」が３％程度の高い値であっても、「断面２次モーメント比（％）」が低い値であればリーニング不良は発生しないし、事実そのようなワイヤは多く確認されている。
よって、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」からはリーニング不良を予測することはできず、ボンディングワイヤを選別することができない。また、最終線引きダイヤモンド・ダイスを管理することもできない。
つまり、「断面２次モーメント比（％）」を管理値とし、最終線引きダイヤモンド・ダイスやワイヤを識別する方法で、リーニング不良を管理することが可能になる。リーニング不良は、使用されるワイヤ線径、パッケージ種類、ボンディング条件などによって許容値が変化するので「断面２次モーメント比（％）」の固定値を限定するのは容易でないが、図９より１％以下に管理することで極度なリーニング不良を抑えることが可能であると考えられる。 Next, using the six types of wires of Example 2, using a wire bonder (UTC-400 type) manufactured by Shinkawa Co., Ltd., in the atmosphere, a molten ball (ball diameter: 38 μm) with a discharge time of 0.5 milliseconds. Was bonded to a 100 μm square pure Al pad with a crimped diameter of 45 μm under a predetermined loop condition (height: 300 μm, length: 4 mm) 10,000 times, resulting in a leaning failure as shown in FIG. It was. The results of this leaning failure (number) are shown in FIG. 8 and FIG. 9 as a correlation between “value obtained by dividing difference between wire maximum diameter and minimum diameter by wire diameter (%)” and “second moment ratio (%)”. Shown in According to FIG. 8, the correlation coefficient between “leaning failure (number)” and “value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)” is as low as 0.64. The correlation coefficient between “leaning failure (number)” and “second moment ratio (%)” in FIG. 9 is as high as 0.97, which is found to be distributed almost on a straight line.
Accordingly, the occurrence of the leaning defect is limited to the elliptical wire, and the “secondary moment ratio (%)” is an essential condition for identifying the elliptical wire. In other words, even if the “value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)” is a high value of about 3%, the “secondary moment ratio (%)” is a low value. If this is the case, no leaning will occur and in fact many such wires have been identified.
Therefore, a “leaning failure” cannot be predicted from “a value (%) obtained by dividing the difference between the maximum diameter and the minimum diameter by the wire diameter”, and the bonding wires cannot be selected. Also, the final drawing diamond dies cannot be managed.
That is, it becomes possible to manage the leaning defect by a method of identifying the final drawing diamond die or wire by using “cross-sectional second moment ratio (%)” as a management value. In the case of the leaning defect, the allowable value varies depending on the wire diameter used, the package type, the bonding conditions, etc., so it is not easy to limit the fixed value of the “secondary moment ratio (%)”. It is considered that it is possible to suppress extreme leaning defects by managing to less than%.

断面２次モーメント比（％）とワイヤ最大直径と最小直径の差をワイヤ線径で除した値との関係を示す実施例。The Example which shows the relationship between a cross-sectional secondary moment ratio (%) and the value which remove | divided the difference of the wire maximum diameter and the minimum diameter by the wire diameter. Ａ〜Ｆ：円周と直交する半径方向だけを実測値より３０倍に拡大した断面形状を示す実施例。A to F: Examples showing a cross-sectional shape in which only a radial direction orthogonal to the circumference is enlarged 30 times from an actual measurement value. ワイヤ断面を１６分割した円周部分を示す実施例模式図。The Example schematic diagram which shows the circumferential part which divided the wire cross section into 16 parts. ワイヤ断面を等分割して測定した半径ｒから円周部分の高さ及び幅を算出する模式図。The schematic diagram which calculates the height and width | variety of a circumference part from the radius r measured by equally dividing a wire cross section. ワイヤ断面を長方形に近似して、断面Ｎ（２）次モーメントの近似値を算出する模式説明図。Schematic explanatory drawing which approximates a wire cross section to a rectangle and calculates an approximate value of a cross-section N (2) second moment. 断面2次モーメント比（％）とワイヤ最大直径と最小直径の差をワイヤ線径で除した値（Ovality）との関係を示す実施例。Example showing the relationship between the cross-section second moment ratio (%) and the value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (Ovality). Ｇ〜Ｌ：円周と直交する半径方向だけを実測値より３０倍に拡大した断面形状を示す実施例。G to L: Examples showing a cross-sectional shape in which only the radial direction orthogonal to the circumference is enlarged 30 times from the actual measurement value. ワイヤ最大直径と最小直径の差とリーニング不良との関係を示す実施例。The Example which shows the relationship between the difference of a wire maximum diameter and the minimum diameter, and leaning defect. 本発明の実施例で、断面２次モーメント比（％）とリーニング不良との関係を示す実施例。The Example which shows the relationship between a cross-sectional secondary moment ratio (%) and a leaning defect in the Example of this invention. ボンディングワイヤをループ形成した場合に発生するリーニング不良を真上からみた（特開２００４−１４６７１５号公報掲載図）図。The figure which looked at the leaning defect which generate | occur | produces when a bonding wire is loop-formed from right above (Japanese Unexamined Patent Publication No. 2004-146715 publication).

上記の課題を解決するための、本発明のボンディング前に予測する選別方法は、
以下の通りである。
（ａ） 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおけるリーニング不良の選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面２次モーメントを求める工程、
３） その求められた断面２次モーメントの最大値と最小値とを比較する工程によって、
ボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。
（ｂ） 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおける異形断面ワイヤ及び楕円ワイヤの選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面２次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における軸方向断面２次モーメントの最大値と最小値を求める工程、
４） その求められた線径の最大値と最小値との差をX座標とし、その断面２次モーメントの最大値と最小値との差をY座標としてプロットして比較する工程によって、
ボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。
（ｃ）半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面２次モーメントを求める工程、
３） その求められた断面２次モーメントの最大値と最小値とを比較する工程によって、ボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の適否を判定する管理方法。
（ｄ）半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面２次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における断面２次モーメントの最大値と最小値を求める工程、
４） その線径の最大値と最小値との差およびその断面２次モーメントの最大値と最小値との差を求める工程、
５） その求められた線径の最大値と最小値との差をX座標としその断面２次モーメントの最大値と最小値との差をY座標としてプロットして比較する工程によって、
ボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の適否を判定する管理方法。 In order to solve the above problems, a screening method for predicting before bonding of the present invention is as follows.
It is as follows.
(A) A method for selecting a leaning defect in a bonding wire that three-dimensionally connects between a semiconductor chip and a terminal such as a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) a step of integrating each of the divided axial directions of the circumferential portion using the wire diameter to obtain a cross-sectional secondary moment in the direction;
3) By comparing the maximum value and the minimum value of the obtained cross-sectional secondary moment,
A bonding wire selection method for determining a leaning defect in loop formation when bonding wires are connected.
(B) A method for selecting a deformed cross-section wire and an elliptical wire in a bonding wire for connecting three-dimensionally between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) a step of integrating each of the divided axial directions of the circumferential portion using the wire diameter to obtain a cross-sectional secondary moment in the direction;
3) a step of obtaining the maximum value and the minimum value of the wire diameter from the measured values at the circumferential portion, and the maximum value and the minimum value of the axial moment of inertia in the circumferential portion,
4) By plotting and comparing the difference between the maximum value and minimum value of the obtained wire diameter as the X coordinate and the difference between the maximum value and minimum value of the sectional secondary moment as the Y coordinate,
A bonding wire selection method for determining a leaning defect in loop formation when bonding wires are connected.
(C) A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) Step of integrating for each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional secondary moment in the direction;
3) that by comparing the maximum value of the obtained moment of inertia and the minimum value, it determines how to manage the appropriateness of the bearing portion in the diamond die for final wire drawing the bonding wire.
(D) A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) Step of integrating for each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional secondary moment in the direction;
3) obtaining a maximum value and a minimum value of the wire diameter in the circumference portion from the measured values, and a maximum value and a minimum value of a cross-sectional secondary moment in the circumference portion;
4) A step of obtaining a difference between the maximum value and the minimum value of the wire diameter and a difference between the maximum value and the minimum value of the secondary moment of the section,
5) the step of the difference between the maximum value and the minimum value of the calculated resulting wire diameter and X-coordinate difference between the maximum value and the minimum value of the second moment is plotted as the Y coordinate comparison,
A management method for determining the suitability of a bearing part in a diamond die for final drawing of a bonding wire.

純度９９．９９９質量％以上の高純度金へ微量元素を所定量含有させて純度９９．９９質量％以上の高純度金を調製した。この調製品を真空溶解炉で溶解鋳造し、伸線加工した。そして、最終線径２３μｍのところで、孔形状を異ならせた６種類のダイヤモンド・ダイス（公称径はいずれも23μｍである。）を用意して６種類の極細線を作成し、それぞれ最終熱処理した。この６種類のワイヤの外径をレーザ回折を利用した線径測定器によって各々測定した。このような線径測定器としては、株式会社キーエンス製のデジタル寸法測定器（LS-7000）や東京光電子工業株式会社製のレーザマイクロゲージ D5やCERSA社製のLDSN-200等を利用できる。
６種類のワイヤ径の測定結果を図１のプロットＡ〜Ｆに示す。また、ワイヤ断面の半
径方向を拡大した断面形状を図２のA〜Fに示す。図１のプロットＡ〜Ｆは、図２のプロットＡ〜Ｆに対応する。ここで、Ｏｖａｌｉｔｙとは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」をいい、１００×（（ボンディングワイヤの線径の最大値）−（ボンディングワイヤの線径の最小値））／（ボンディングワイヤの線径）と定義し、「断面2次モーメント比（％）」は、ボンディングワイヤの断面2次モーメントを半周１８０度に対して１１．２５度ステップで１６箇所測定した中で最大値と最小値を求め、１００×（最大値−最小値）／（最大値）によって定義した。
断面２次モーメントは次のようにして得られる。
ワイヤ断面を図３の半円に示すように１１．５度ステップで１６の円周部分に等分割して、それぞれの円周部分ごとに直径を測定し、それぞれの半径ｒを求める。
測定された半径ｒから図４に示すように各円周部分の半径ｒに対応する、Ｘ軸に対する高さｙ、及びＸ軸に投影した幅がそれぞれ、ｒ sinθ及びｒ cos θから得られる。
具体的には、高さｙは分割された円周部分の中点のθ値とその測定されたｒ値から、或いはその円周範囲を更に細分したθとそのｒ測定値から算出した平均値などで近似し、幅のｘ値はこれら円周部分の前後のθ値とそのｒ値によりそれぞれのｘ値を算出して引き算することによりその間の幅として得られる。
このようにして得られた各円周部分毎のｘ、ｙ値から長方形に近似した断面形状を表すと、図５のようになる。このように近似した個々の断面形状に対する断面２次モーメントを積算することにより、ワイヤ断面としての２次モーメントを求めることができる。
以下、同様にして順次分割数１６に対応して１１．５度づつずらしてそれぞれの方向毎の半円の断面２次モーメントを求めることができる。
以上の説明においては、ワイヤ断面を等分割してそれぞれの半径方向毎に長方形状に近似して、それぞれの長方形の断面２次モーメントの和としてワイヤ断面の２次モーメントを求めたが、これらはワイヤ断面の２次モーメントとしてＸＹ座標上の積分値にほかならない。
これらの分割数は１６に限るものではないが、分割間隔を大きくすると断面形状を正確に反映できないので、概ね１６以上に分割して計測することが好ましい。
また、図２の濃い実線と薄い実線は、ワイヤ断面の半円形状を示し、同じワイヤの測定位置をワイヤの長手方向に10ｍずらして変化させ2回測定した結果である。また、下中央部の四角はワイヤ断面の中心点である。
図１のＡ〜Ｆの６種類のワイヤ径の測定結果と、ワイヤ断面の半径方向を拡大した図２のＡ〜Ｆの断面形状を比較しながら参照すると、（１）図１のAプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面2次モーメント比（％）」はいずれも低い値であり、図２−Ａから真円に近い形状である。（２）図１−Ｃ、Ｆプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面2次モーメント比（％）」はいずれも増加しており、図２−Ｃ、Ｆから楕円に近い形状であることが確認できる。（３）一方、図１―Ｂ、Ｄ、Ｅフ゜ロットは、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」が増加しても、「断面2次モーメント比（％）」の増加は小さく、図２−Ｂ、Ｄ、Ｅから多角形に近い形状である。
したがって、（１）〜（３）のプロットの関係から、「断面２次モーメント」又は「断面２次モーメント比（％）」の大小によって、楕円ワイヤと多角形ワイヤとを識別することができる。 A predetermined amount of a trace element was contained in high-purity gold having a purity of 99.999% by mass or more to prepare high-purity gold having a purity of 99.99% by mass or more. This preparation was melt cast in a vacuum melting furnace and drawn. Then, at the final wire diameter of 23 μm, six types of diamond dies having different hole shapes (the nominal diameter is 23 μm) were prepared to prepare six types of ultrafine wires, and each was subjected to final heat treatment. The outer diameters of these six types of wires were measured with a wire diameter measuring device using laser diffraction. As such a wire diameter measuring device, a digital dimension measuring device (LS-7000) manufactured by Keyence Corporation, a laser micro gauge D5 manufactured by Tokyo Koden Kogyo Co., Ltd., LDSN-200 manufactured by CERSA, or the like can be used.
The measurement results of the six types of wire diameters are shown in plots A to F in FIG. Moreover, the cross-sectional shape which expanded the radial direction of the wire cross section is shown to AF of FIG. The plots A to F in FIG. 1 correspond to the plots A to F in FIG. Here, “Ovality” means “value obtained by dividing the difference between the maximum wire diameter and the minimum diameter by the wire diameter (%)”, and 100 × ((maximum value of the wire diameter of the bonding wire) − (the wire diameter of the bonding wire). ) / (Bonding wire diameter), and “cross section secondary moment ratio (%)” is 16 in steps of 11.25 degrees with respect to the cross section secondary moment of bonding wire of 180 degrees per half circumference. The maximum value and the minimum value were obtained among the points measured and defined by 100 × (maximum value−minimum value) / (maximum value).
The cross-sectional second moment is obtained as follows.
As shown in the semicircle of FIG. 3, the wire cross section is equally divided into 16 circumferential portions in 11.5 degree steps, the diameter is measured for each circumferential portion, and each radius r is obtained.
From the measured radius r, as shown in FIG. 4, the height y with respect to the X axis and the width projected on the X axis corresponding to the radius r of each circumferential portion are obtained from r sin θ and r cos θ, respectively.
Specifically, the height y is the average value calculated from the θ value at the midpoint of the divided circumferential portion and the measured r value , or from θ and the r measured value obtained by further subdividing the circumferential range. The x value of the width is obtained as the width between them by calculating and subtracting the respective x values from the θ values before and after these circumferential portions and their r values.
FIG. 5 shows a cross-sectional shape approximated to a rectangle from the x and y values for each circumferential portion thus obtained. By integrating the second moment for the individual cross-sectional shape similar as described above, it is possible to obtain the secondary moment of the wire cross-section.
In the same manner, the second-order moment of the semicircle in each direction can be obtained by shifting by 11.5 degrees sequentially corresponding to the division number of 16.
In the above description, the wire cross-section is equally divided and approximated to a rectangular shape for each radial direction, and the secondary moment of the wire cross-section is obtained as the sum of the cross-sectional second moments of each rectangle. The second moment of the wire cross section is nothing but an integral value on the XY coordinates.
The number of divisions is not limited to 16, but if the division interval is increased, the cross-sectional shape cannot be accurately reflected. Therefore, it is preferable to divide the measurement into approximately 16 or more.
Also, the dark solid line and the thin solid line in FIG. 2 indicate the semicircular shape of the wire cross section, and are the results of measuring twice by changing the measurement position of the same wire by shifting it by 10 m in the longitudinal direction of the wire. The square at the lower center is the center point of the wire cross section.
When comparing the measurement results of the six types of wire diameters A to F in FIG. 1 with the cross-sectional shapes of A to F in FIG. 2 in which the radial direction of the wire cross section is enlarged, (1) A plot in FIG. “Value obtained by dividing difference between wire maximum diameter and minimum diameter by wire wire diameter (%)” and “cross section secondary moment ratio (%)” are both low values, and a shape close to a perfect circle from FIG. It is. (2) Figures 1-C and F plots show that both "value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)" and "secondary moment ratio (%)" are increasing. 2-C and F, it can be confirmed that the shape is close to an ellipse. (3) On the other hand, in Fig. 1-B, D and E plots, even if the "value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)" increases, %) ”Is small, which is a shape close to a polygon from FIGS.
Therefore, the elliptical wire and the polygonal wire can be identified from the relationship of the plots of (1) to (3) depending on the magnitude of the “secondary moment of section” or “ratio of second moment of section (%)”.

本発明は、基本的に上記のリーニング不良をボンディング工程で発生させないためになされたものである。すなわち、本発明は、これまでボンディングワイヤの結線時のループ形成においてリーニング不良がなぜ生じるのか明らかでなかった原因を解明することによってなされたものである。本発明者らはこの解明過程で、楕円を含む歪んだ形状の異形断面ワイヤはワイヤ最大直径と最小直径の差またはワイヤ最大直径と最小直径の差をワイヤ線径で除した値が断面二次モーメント比と比例関係にあることを見いだし、多角形ワイヤには比例関係が無いことを確認した。ワイヤ最大直径と最小直径の差と断面２次モーメント比を利用することにより、これまで楕円ワイヤと多角形ワイヤとを分類分けし、識別することができなかった課題の解決に成功した。また、本発明者らはリーニング不良の原因がボンディングワイヤの断面形状と関連することを解明し、結線前の段階でボンディングワイヤを選別することによってリーニング不良の解決に成功した。また、リーニング不良がボンディングワイヤを介して最終ダイヤモンド・ダイスのベアリング部の形状と関連していることがわかったので、最終線引きダイヤモンド・ダイスを管理することによってリーニング不良を解決する方法を解明した。 The present invention is basically made in order to prevent the above-mentioned leaning defect from occurring in the bonding process. That is, the present invention has been made by elucidating the cause that has not been clarified why the leaning failure has occurred in the loop formation when bonding wires are connected. In this elucidation process, the present inventors have found that a deformed cross-section wire including an ellipse is obtained by dividing the difference between the maximum wire diameter and the minimum wire diameter or the difference between the wire maximum diameter and the minimum wire diameter by the wire diameter. It was found that there was a proportional relationship with the moment ratio, and it was confirmed that the polygonal wire had no proportional relationship. By utilizing the difference between the maximum diameter and the minimum diameter of the wire and the second moment ratio, the elliptical wire and the polygonal wire were classified and succeeded in solving the problems that could not be identified. In addition, the present inventors have clarified that the cause of the leaning failure is related to the cross-sectional shape of the bonding wire, and succeeded in solving the leaning failure by selecting the bonding wire before connection. Also, since it was found that the leaning defect was related to the shape of the bearing part of the final diamond die through the bonding wire, the method for solving the leaning defect by managing the final drawing diamond die was clarified.

純度９９．９９９質量％以上の高純度金へ微量元素を所定量含有させて純度９９．９９質量％以上の高純度金を調製した。この調製品を真空溶解炉で溶解鋳造し、伸線加工した。そして、最終線径２３μｍのところで、孔形状を異ならせた６種類のダイヤモンド・ダイス（公称径はいずれも23μｍである。）を用意して６種類の極細線を作成し、それぞれ最終熱処理した。この６種類のワイヤの外径をレーザ回折を利用した線径測定器によって各々測定した。このような線径測定器としては、株式会社キーエンス製のデジタル寸法測定器（LS-7000）や東京光電子工業株式会社製のレーザマイクロゲージ D5やCERSA社製のLDSN-200等を利用できる。
６種類のワイヤ径の測定結果を図１のプロットＡ〜Ｆに示す。また、ワイヤ断面の半
径方向を拡大した断面形状を図２のA〜Fに示す。図１のプロットＡ〜Ｆは、図２のプロットＡ〜Ｆに対応する。ここで、Ｏｖａｌｉｔｙとは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」をいい、１００×（（ボンディングワイヤの線径の最大値）−（ボンディングワイヤの線径の最小値））／（ボンディングワイヤの線径）と定義し、「断面2次モーメント比（％）」は、ボンディングワイヤの断面2次モーメントを半周１８０度に対して１１．２５度ステップで１６箇所測定した中で最大値と最小値を求め、１００×（最大値−最小値）／（最大値）によって定義した。
断面２次モーメントは次のようにして得られる。
ワイヤ断面を図３の半円に示すように１１．５度ステップで１６の円周部分に等分割して、それぞれの円周部分ごとに直径を測定し、それぞれの半径ｒを求める。
測定された半径ｒから図４に示すように各円周部分の半径ｒに対応する、Ｘ軸に対する高さｙ、及びＸ軸に投影した幅がそれぞれ、ｒ sinθ及びｒ cos θから得られる。
具体的には、高さｙは分割された円周部分の中点のθ値とその測定されたｒ値から、或いはその円周範囲を更に細分したθとそのｒ測定値から算出した平均値などで近似し、幅のｘ値はこれら円周部分の前後のθ値とそのｒ値によりそれぞれのｘ値を算出して引き算することによりその間の幅として得られる。
このようにして得られた各円周部分毎のｘ、ｙ値から長方形に近似した断面形状を表すと、図５のようになる。このように近似した個々の断面形状に対する断面２次モーメントを積算することにより、ワイヤ断面としての２次モーメントを求めることができる。
以下、同様にして順次分割数１６に対応して１１．５度づつずらしてそれぞれの方向毎の半円の断面２次モーメントを求めることができる。
以上の説明においては、ワイヤ断面を等分割してそれぞれの半径方向毎に長方形状に近似して、それぞれの長方形の断面２次モーメントの和としてワイヤ断面の２次モーメントを求めたが、これらはワイヤ断面の２次モーメントとしてＸＹ座標上の積分値にほかならない。
これらの分割数は１６に限るものではないが、分割間隔を大きくすると断面形状を正確に反映できないので、概ね１６以上に分割して計測することが好ましい。
また、図２の濃い実線と薄い実線は、ワイヤ断面の半円形状を示し、同じワイヤの測定位置をワイヤの長手方向に10ｍずらして変化させ2回測定した結果である。また、下中央部の四角はワイヤ断面の中心点である。
図１のＡ〜Ｆの６種類のワイヤ径の測定結果と、ワイヤ断面の半径方向を拡大した図２のＡ〜Ｆの断面形状を比較しながら参照すると、（１）図１のAプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面2次モーメント比（％）」はいずれも低い値であり、図２−Ａから真円に近い形状である。（２）図１−Ｃ、Ｆプロットは「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」と「断面2次モーメント比（％）」はいずれも増加しており、図２−Ｃ、Ｆから楕円に近い形状であることが確認できる。（３）一方、図１―Ｂ、Ｄ、Ｅフ゜ロットは、「ワイヤ最大直径と最小直径の差をワイヤ線径で除した値（％）」が増加しても、「断面2次モーメント比（％）」の増加は小さく、図２−Ｂ、Ｄ、Ｅから多角形に近い形状である。
したがって、（１）〜（３）のプロットの関係から、「断面２次モーメント」又は「断面２次モーメント比（％）」の大小によって、楕円ワイヤと多角形ワイヤとを識別することができる。 A predetermined amount of a trace element was contained in high-purity gold having a purity of 99.999% by mass or more to prepare high-purity gold having a purity of 99.99% by mass or more. This preparation was melt cast in a vacuum melting furnace and drawn. Then, at the final wire diameter of 23 μm, six types of diamond dies having different hole shapes (the nominal diameter is 23 μm) were prepared to prepare six types of ultrafine wires, and each was subjected to final heat treatment. The outer diameters of these six types of wires were measured with a wire diameter measuring device using laser diffraction. As such a wire diameter measuring device, a digital dimension measuring device (LS-7000) manufactured by Keyence Corporation, a laser micro gauge D5 manufactured by Tokyo Koden Kogyo Co., Ltd., LDSN-200 manufactured by CERSA, or the like can be used.
The measurement results of the six types of wire diameters are shown in plots A to F in FIG. Moreover, the cross-sectional shape which expanded the radial direction of the wire cross section is shown to AF of FIG. The plots A to F in FIG. 1 correspond to the plots A to F in FIG. Here, “Ovality” means “value obtained by dividing the difference between the maximum wire diameter and the minimum diameter by the wire diameter (%)”, and 100 × ((maximum value of the wire diameter of the bonding wire) − (the wire diameter of the bonding wire). ) / (Bonding wire diameter), and “cross section secondary moment ratio (%)” is 16 in steps of 11.25 degrees with respect to the cross section secondary moment of bonding wire of 180 degrees per half circumference. The maximum value and the minimum value were obtained among the points measured and defined by 100 × (maximum value−minimum value) / (maximum value).
The cross-sectional second moment is obtained as follows .
As shown in the semicircle of FIG. 3, the wire cross section is equally divided into 16 circumferential portions in 11.5 degree steps, the diameter is measured for each circumferential portion, and each radius r is obtained.
From the measured radius r, as shown in FIG. 4, the height y with respect to the X axis and the width projected on the X axis corresponding to the radius r of each circumferential portion are obtained from r sin θ and r cos θ, respectively.
Specifically, the height y is the average value calculated from the θ value at the midpoint of the divided circumferential portion and the measured r value , or from θ and the r measured value obtained by further subdividing the circumferential range. The x value of the width is obtained as the width between them by calculating and subtracting the respective x values from the θ values before and after these circumferential portions and their r values.
FIG. 5 shows a cross-sectional shape approximated to a rectangle from the x and y values for each circumferential portion thus obtained. By integrating the second moment for the individual cross-sectional shape similar as described above, it is possible to obtain the secondary moment of the wire cross-section.
In the same manner, the second-order moment of the semicircle in each direction can be obtained by shifting by 11.5 degrees sequentially corresponding to the division number of 16.
In the above description, the wire cross-section is equally divided and approximated to a rectangular shape for each radial direction, and the secondary moment of the wire cross-section is obtained as the sum of the cross-sectional second moments of each rectangle. The second moment of the wire cross section is nothing but an integral value on the XY coordinates.
The number of divisions is not limited to 16, but if the division interval is increased, the cross-sectional shape cannot be accurately reflected. Therefore, it is preferable to divide the measurement into approximately 16 or more.
Also, the dark solid line and the thin solid line in FIG. 2 indicate the semicircular shape of the wire cross section, and are the results of measuring twice by changing the measurement position of the same wire by shifting it by 10 m in the longitudinal direction of the wire. The square at the lower center is the center point of the wire cross section.
When comparing the measurement results of the six types of wire diameters A to F in FIG. 1 with the cross-sectional shapes of A to F in FIG. 2 in which the radial direction of the wire cross section is enlarged, (1) A plot in FIG. “Value obtained by dividing difference between wire maximum diameter and minimum diameter by wire wire diameter (%)” and “cross section secondary moment ratio (%)” are both low values, and a shape close to a perfect circle from FIG. It is. (2) Figures 1-C and F plots show that both "value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)" and "secondary moment ratio (%)" are increasing. 2-C and F, it can be confirmed that the shape is close to an ellipse. (3) On the other hand, in Fig. 1-B, D and E plots, even if the "value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (%)" increases, %) ”Is small, which is a shape close to a polygon from FIGS.
Therefore, the elliptical wire and the polygonal wire can be identified from the relationship of the plots of (1) to (3) depending on the magnitude of the “secondary moment of section” or “ratio of second moment of section (%)”.

断面2次モーメント比（％）とワイヤ最大直径と最小直径の差をワイヤ線径で除した値との関係を示す実施例。Example showing the relationship between the sectional moment of inertia ratio (%) and the value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter. Ａ〜Ｆ：円周と直交する方向に対し円周方向だけを実測値より３０倍に拡大した断面形状を示す実施例。A to F: Examples showing a cross-sectional shape in which only the circumferential direction is expanded 30 times from the actual measurement value with respect to the direction orthogonal to the circumference. ワイヤ断面を１６分割した円周部分を示す実施例模式図。The Example schematic diagram which shows the circumferential part which divided the wire cross section into 16 parts. ワイヤ断面を等分割して測定した半径ｒ から円周部分の高さ及び幅を算出する模式図。The schematic diagram which calculates the height and width | variety of a circumference part from radius r measured by equally dividing a wire cross section. ワイヤ断面を長方形に近似して、断面２次モーメントの近似値を算出する模式説明図。The model explanatory drawing which approximates a wire cross section to a rectangle and calculates the approximate value of a cross-section secondary moment. 断面2次モーメント比（％）とワイヤ最大直径と最小直径の差をワイヤ線径で除した値（Ovality）との関係を示す実施例。Example showing the relationship between the cross-section second moment ratio (%) and the value obtained by dividing the difference between the maximum and minimum wire diameters by the wire diameter (Ovality). Ｇ〜Ｌ：円周と直交する方向に対し円周方向だけを実測値より３０倍に拡大した断面形状を示す実施例。G to L: Examples showing a cross-sectional shape in which only the circumferential direction is enlarged 30 times from the actual measurement value with respect to the direction orthogonal to the circumference. ワイヤ最大直径と最小直径の差とリーニング不良との関係を示す実施例。The Example which shows the relationship between the difference of a wire maximum diameter and the minimum diameter, and a leaning defect. 本発明の実施例で、断面2次モーメント比（％）とリーニング不良との関係を示す実施例。The Example which shows the relationship between a cross-sectional secondary moment ratio (%) and a leaning defect in the Example of this invention. ボンディングワイヤをループ形成した場合に発生するリーニング不良を真上からみた（特開２００４−１４６７１５号公報掲載図）図。The figure which looked at the leaning defect which generate | occur | produces when a bonding wire is loop-formed from right above (Japanese Unexamined Patent Publication No. 2004-146715 publication).

Claims (6)

半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおけるリーニング不良品の選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分してワイヤ断面の当該方向におけるそれぞれの断面Ｎ次モーメントを求める工程、および
３） その求められた断面Ｎ次モーメントの最大値と最小値とを比較する工程、
からなる一連の選別工程によってボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。 A method for selecting a defective product in a bonding wire for three-dimensionally connecting between a semiconductor chip and a terminal such as a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) a step of integrating each of the divided axial directions of the circumferential portion using the wire diameter value to obtain each section N-th moment in the direction of the wire section, and 3) the section N-order obtained Comparing the maximum and minimum moment values,
A bonding wire sorting method for determining a leaning defect in loop formation when bonding wires are connected by a series of sorting steps. 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤにおける楕円を含む異形断面形状ワイヤの選別方法であって、
１） 結線前のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分してワイヤ断面の当該方向におけるそれぞれの断面Ｎ次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における断面Ｎ次モーメントの最大値と最小値を求める工程、
４） その線径の最大値と最小値との差およびその断面Ｎ次モーメントの最大値と最小値との差を求める工程、および
５） その求められた線径の最大値と最小値との差をＸ座標としその断面Ｎ次モーメントの最大値と最小値との差をＹ座標としてプロットして比較する工程、
からなる一連の選別工程によってボンディングワイヤの結線時のループ形成におけるリーニング不良を判定するボンディングワイヤの選別方法。 A method for selecting a deformed cross-sectional shape wire including an ellipse in a bonding wire for connecting three-dimensionally between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire before connection and measuring the diameter of the divided circumferential portion;
2) A step of integrating each of the divided axial directions of the circumferential portion using the wire diameter value to obtain each section N-th moment in the direction of the wire section;
3) A step of obtaining a maximum value and a minimum value of the wire diameter in the circumferential portion and a maximum value and a minimum value of the cross-sectional N-th moment in the circumferential portion from the measured values,
4) a step of obtaining a difference between the maximum value and the minimum value of the wire diameter and a difference between the maximum value and the minimum value of the cross-sectional N-th moment, and 5) the maximum value and the minimum value of the obtained wire diameter. Plotting and comparing the difference between the maximum value and the minimum value of the N-th moment of the cross section as the X coordinate as the Y coordinate,
A bonding wire sorting method for determining a leaning defect in loop formation when bonding wires are connected by a series of sorting steps. 前記の断面Ｎ次モーメントとして２次モーメントを用い、その最大値と最小値との比較を、最大値と最小値との差を最大値または最小値で除したときの断面２次モーメント比で評価することを特徴とする請求項１または２に記載のボンディングワイヤの選別方法。 The second moment is used as the N-th moment of the cross section, and the comparison between the maximum value and the minimum value is evaluated by the cross-section second moment ratio when the difference between the maximum value and the minimum value is divided by the maximum value or the minimum value. The bonding wire selecting method according to claim 1, wherein the bonding wire is selected. 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、および
３） その求められた断面Ｎ次モーメントの最大値と最小値とを比較する工程、
からなる一連の管理工程によって適否を判定するボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の管理方法。 A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) a step of integrating for each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional Nth moment in the direction; and 3) a maximum value of the obtained cross-sectional Nth moment Comparing the minimum value,
A method for managing a bearing portion in a diamond die for final drawing of a bonding wire for determining suitability by a series of management steps. 半導体チップとリードフレーム等の端子間を３次元的に結線するボンディングワイヤ用ダイヤモンド・ダイスの管理方法であって、
１） ダイヤモンド・ダイス引き加工後のボンディングワイヤの全周を微細に分割し、その分割された円周部分の線径を測定する工程、
２） その線径値を用いて円周部分の各分割された軸方向毎に積分し、当該方向における断面Ｎ次モーメントを求める工程、
３） それらの測定値から当該円周部分における線径の最大値と最小値、および当該円周部分における断面Ｎ次モーメントの最大値と最小値を求める工程、
４） その線径の最大値と最小値との差およびその断面Ｎ次モーメントの最大値と最小値との差を求める工程、および
５） その求められた線径の最大値と最小値との差をＸ座標としその断面Ｎ次モーメントの最大値と最小値との差をＹ座標としてプロットして比較する工程、
からなる一連の管理工程によって適否を判定するボンディングワイヤを最終線引き加工するためのダイヤモンド・ダイスにおけるベアリング部の管理方法。 A method for managing diamond dies for bonding wires that three-dimensionally connects between terminals such as a semiconductor chip and a lead frame,
1) A step of finely dividing the entire circumference of the bonding wire after diamond and die drawing, and measuring the diameter of the divided circumferential portion,
2) A step of integrating each divided axial direction of the circumferential portion using the wire diameter value to obtain a cross-sectional Nth moment in the direction,
3) A step of obtaining a maximum value and a minimum value of the wire diameter in the circumferential portion and a maximum value and a minimum value of the cross-sectional N-th moment in the circumferential portion from the measured values,
4) a step of obtaining a difference between the maximum value and the minimum value of the wire diameter and a difference between the maximum value and the minimum value of the cross-sectional N-th moment, and 5) the maximum value and the minimum value of the obtained wire diameter. Plotting and comparing the difference between the maximum value and the minimum value of the N-th moment of the cross section as the X coordinate as the Y coordinate,
A method for managing a bearing portion in a diamond die for final drawing of a bonding wire for determining suitability by a series of management steps. 前記の断面Ｎ次モーメントとして２次モーメントを用い、その最大値と最小値との比較を、最大値と最小値との差を最大値または最小値で除したときの断面２次モーメント比で評価することを特徴とする請求項４または５に記載のボンディングワイヤダイヤモンド・ダイスにおけるベアリング部の管理方法。 The second moment is used as the N-th moment of the cross section, and the comparison between the maximum value and the minimum value is evaluated by the cross-section second moment ratio when the difference between the maximum value and the minimum value is divided by the maximum value or the minimum value. The method for managing a bearing portion in a bonding wire diamond die according to claim 4 or 5, wherein:
JP2006089531A 2006-03-28 2006-03-28 Bonding wire selection method and diamond / die management method for bonding wire Expired - Fee Related JP3905914B1 (en)

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SG200701971-4A SG136082A1 (en) 2006-03-28 2007-03-16 Sorting method of bonding wire and management method of diamond dice for bonding wire
TW096109830A TWI337774B (en) 2006-03-28 2007-03-22 Sorting method of bonding wire drawn by diamond dice and management method for diamond dice
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