JP3753685B2 - Wire bonding method - Google Patents
Wire bonding method Download PDFInfo
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- JP3753685B2 JP3753685B2 JP2002272617A JP2002272617A JP3753685B2 JP 3753685 B2 JP3753685 B2 JP 3753685B2 JP 2002272617 A JP2002272617 A JP 2002272617A JP 2002272617 A JP2002272617 A JP 2002272617A JP 3753685 B2 JP3753685 B2 JP 3753685B2
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- electrode
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- 238000000034 method Methods 0.000 title claims description 33
- 239000004065 semiconductor Substances 0.000 claims description 46
- 239000002184 metal Substances 0.000 description 15
- 238000010586 diagram Methods 0.000 description 4
- 230000000630 rising effect Effects 0.000 description 3
- 238000002788 crimping Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
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Description
【0001】
【発明の属する技術分野】
本発明は電極間をワイヤで接続するワイヤボンディング方法に関し、より詳細にはスティッチボンディングした部分に重ねてボールボンディングを行ってワイヤと電極との固着を補強するワイヤボンディング方法に関するものである。
【0002】
【従来の技術】
近年、半導体発光装置を始め半導体装置の薄型化が種々検討されている。その中の一つの方法として、図5に示すような半導体素子3を回路基板1に実装する場合に、回路基板1に形成された電極2にワイヤ4をボールボンディングした後、半導体素子3の上面電極31にスティッチボンディングするワイヤボンディング方法が提案されている(例えば特許文献1参照)。この提案されているワイヤボンディング方法によれば、ボールボンディング部Bにおいて生じるワイヤ4の立ち上がり部分が、ちょうど半導体素子3の高さで相殺されるかたちになるので、半導体素子3の上面電極31にワイヤ4を第1ボンドした後、回路基板1の電極2に第2ボンドしていた従来の方法に比べて半導体装置の一層の薄型化を図ることができる。
【0003】
一方、このワイヤボンディング方法は、ボンディングに方向性がなく作業性に優れているものの、スティッチボンディング部Sはボールボンディング部Bに比べ圧着面積が小さく、また圧着部の厚さが薄いため、接合強度が弱いという本質的な問題があった。本発明者が経験したところによれば、その理由は未だ明らかになっていないが、半導体素子の上面電極にワイヤをスティッチボンディングした場合に、特にワイヤが切れやすいという問題があった。
【0004】
そこで、スティッチボンディング部Sの固着強度を大きくすることを目的として、スティッチボンディング部Sに重ねてボールボンディングを行うことが提案されている(例えば参考文献2)。
【0005】
【特許文献1】
特開2001−15542号公報(特許請求の範囲の欄、図2)
【特許文献2】
特開平11−163026号公報(特許請求の範囲の欄、図2)
【0006】
【発明が解決しようとする課題】
この方法を図5に示したワイヤボンディング方法に適用すると、ワイヤの固着強度は確かに大きくなるが、図6に示すように、ボールボンディング部B2にワイヤの立ち上がり部分(突起)6が不可避的に残るため、半導体装置の薄型化という目的が充分には達成できなかった。
【0007】
本発明はこのような従来の問題に鑑みてなされたものであり、その目的とするところは、ワイヤと電極との固着、特にワイヤと半導体素子の上面電極との固着を強くでき、且つ半導体装置の薄型化を図れるワイヤボンディング方法を提供することにある。
【0008】
また本発明の目的は、新たな設備を必要とせず、また装置の生産性を低下させることなくワイヤと電極とを強く固着できるワイヤボンディング方法を提供することにある。
【0009】
【課題を解決するための手段】
本発明によれば、キャピラリを用いてワイヤを第1電極にボールボンディングした後、前記キャピラリからワイヤを繰り出しながら前記キャピラリを、半導体素子の上面に形成された、前記第1電極よりも高い位置にある第2電極上に移動させ、この第2電極にワイヤをスティッチボンディングした後、第2電極の前記スティッチボンディングした部分に重ねてボールボンディングを行うワイヤボンディング方法において、前記キャピラリ先端部のフェイス面の半径を、前記半導体素子の上面外周辺から前記第2電極のボールボンディング跡の中心までの最短距離よりも長くするとともに、フェイス面に15°以下の傾斜をもたせ、前記第2電極のボールボンディング跡に形成される突起を、前記フェイス面で押しつぶすことを特徴とするワイヤボンディング方法が提供される。
【0010】
【発明の実施の形態】
本発明者は、スティッチボンディングした部分の固着強度を上げるために、従来と同様にスティッチボンディングした部分に重ねてボールボンディングを行うこととし、これを前提に第2電極にボールボンディングを行うことにより生じる問題、すなわち第2電極のボールボンディング跡に形成される突起を除去できないか検討をした。突起を単に除去するだけならば、例えばワイヤボンディング工程の後に押さえ治具で突起を押しつぶす、あるいは切断治具で突起を切断すればよいが、突起を押しつぶすあるいは切断するためには新たな設備が必要となり、また装置の生産性の低下を招く。そこで既存の設備で前記突起を除去できないかさらに検討した結果、ワイヤボンディング工程で用いられているキャピラリに着目し、このキャピラリを用いて前記突起を押しつぶせばよいことを見出し本発明をなすに至った。
【0011】
すなわち、本発明のワイヤボンディング方法の大きな特徴の一つは、キャピラリ先端部のフェイス面で前記突起を押しつぶすことにある。かかる構成によれば、新たな設備を導入することなくキャピラリの移動制御を変更するだけで前記突起をなくすことができ、生産性の低下も抑えられる。
【0012】
また本発明のもう一つの大きな特徴は、キャピラリのフェイス面の半径を、半導体素子の上面外周辺から第2電極のボールボンディング跡の中心までの最短距離よりも長くしたことにある。図7に示すように、従来のキャピラリ5’のフェイス面51’は半導体素子3の幅よりも小さかったため、フェイス面51’で前記突起6を押しつぶそうとすると、次のワイヤボンディングのために準備されているキャピラリ先端の金属ボールbが半導体素子3と接触するおそれがあった。そこで本発明では、キャピラリのフェイス面の半径を、半導体素子の上面外周辺から前記第2電極のボールボンディング跡の中心までの最短距離よりも長くし、フェイス面で前記突起を押しつぶす際に、キャピラリ先端に形成された金属ボールと半導体素子とが接触しないようにした。なお、半導体素子の上面外周辺から第2電極のボールボンディング跡の中心までの最短距離とは、図8に示すように、ボールボンディング跡の中心Oから、半導体素子3の直近の外周辺に下ろした垂線の長さをいう。
【0013】
本発明で用いるキャピラリは、前記フェイス面の半径を有すると同時に、スティッチボンディングにおいてワイヤを電極に強固に固着する観点からは、フェイス面に15°以下の傾斜をもたせる必要がある。フェイス面の傾斜角が15°より大きいと、フェイス面を介してワイヤに押圧力が充分に加わらず、電極へのワイヤの接着が不十分となるおそれがあるからである。なおフェイス面の傾斜角とは、キャピラリ先端における軸方向に垂直な平面とフェイス面とのなす角をいう。
【0014】
本発明のワイヤボンディング方法の一例を図1に示す。なお、この実施形態ではチップ型半導体装置の場合のワイヤボンディング方法を説明しているが、本発明のワイヤボンディング方法はチップ型半導体装置に限定されるものではなく、従来公知の半導体素子のワイヤボンディングに用いることができる。
【0015】
まず、トーチ電極(不図示)からの放電によって、キャピラリ5先端部の開口部から露出したワイヤ4の先端に金属ボールbを成形する(図1(a))。そしてキャピラリ5を降下させて、基板1上に形成された電極(第1電極)2に、ワイヤ先端の金属ボールbを押し付けて、超音波振動を加えながら金属ボールbを電極2に固着させる(ボールボンディング、同図(b))。次に、キャピラリ5を、半導体素子3の高さよりも少し高い位置まで上昇させながら、基板1上の電極2’に固着された半導体素子3の上方に移動させた後(同図(c))、キャピラリ5を下降させて上面電極(第2電極)31に押し当て、所定の荷重を掛けると同時に超音波振動を加えワイヤ4を上面電極31に固着させる(スティッチボンディング、同図(d))。その後ワイヤ4をクランプした状態でキャピラリ5を上方に移動させてワイヤ4を切断する(同図(e))。
【0016】
次にもう一度、トーチ電極(不図示)からの放電によって、ワイヤ4の先端に金属ボールbを成形する(図2(f))。そしてキャピラリ5を降下させて、半導体素子3の上面電極31のスティッチボンディング部Sに、ワイヤ先端の金属ボールbを押し付けて、超音波振動を加えながら金属ボールbをスティッチボンディング部Sに固着させる(同図(g))。これによりワイヤ4と上面電極31との固着が格段に強くなる。次に、ワイヤ4をクランプした状態でキャピラリ5を上方に移動させてワイヤ4を切断する。このとき、上面電極31のボールボンディング部B2にワイヤ4の立ち上がり部分(突起)6が残る(同図(h))。
【0017】
次のワイヤボンディングのための金属ボールbをワイヤ4の先端に成形した後、突起6の垂直上方にキャピラリ5のフェイス面51が位置し、且つ金属ボールbが半導体素子3に接触しない程度キャピラリ5を水平方向に移動させる(同図(i))。次に、キャピラリ5を下方に移動させて、キャピラリ5のフェイス面51で突起6を押しつぶす(同図(j))。これにより従来装置の薄型化の障害となっていた突起6をなくすことができ、装置の薄型化が図れると同時に、ワイヤ4と上面電極31との固着をより強力にできる。そして次の電極間をワイヤボンディングするためにキャピラリ5を移動させる(同図(k))。
【0018】
突起6を押しつぶす際のキャピラリ5の移動制御は、例えば上面電極31にボールボンディングを行った時にキャピラリ5の平面位置と高さとを記憶しておき、その平面位置情報に基づき、その金属ボールbが半導体素子3に接触しない程度までキャピラリ5を水平方向に移動させ、そして前記高さ情報に基づき、キャピラリ5の下方への移動距離を制御する。このような移動制御によれば、上面電極31の位置や高さがばらついても前記突起6をフェイス面51で確実に押しつぶすことができる。もちろん、キャピラリや上面電極の位置をカメラにより画像として取り込んでデータ処理を行ってキャピラリの移動制御を行っても構わない。
【0019】
一つの半導体素子にワイヤボンディングすべき電極が複数ある場合、ボールボンディング部B2の突起6のキャピラリ5による押しつぶしは、すべての電極間をワイヤボンディングした後に行ってもよいし、一つの電極間をワイヤボンディングした後ごとに順次行ってもよい。キャピラリ5の移動距離を短くし生産効率の上げる観点からは後者が望ましい。
【0020】
次に、本発明のワイヤボンディング方法を、複数の上面電極が形成されているICなどの半導体素子に用いる場合について説明する。図3の半導体装置では、同図(a)に示すように、半導体素子3’の上面外周辺に沿って複数の第2電極31が配設され、この半導体素子3’の周囲を取り巻くように、第2電極31に対応する第1電極(リード)2が配設されている。そしてそれぞれ対応する第1電極2と第2電極31とはワイヤ4で接続される。ワイヤボンディングは前述の通り、キャピラリを用いてまずワイヤ4を第1電極2にボールボンディングし、次に第2電極31にスティッチボンディングした後、さらにスティッチボンディングした部分に重ねてワイヤをボールボンディングする。そして第2電極31に形成された突起6はキャピラリ5のフェイス面51で押しつぶすが、このときキャピラリの先端に形成されている金属ボールbが半導体素子3’およびボンディングしたワイヤ4と接触しないようにするため、図3(b)に示すように、キャピラリ5の軸中心の平面位置は半導体素子3’の側端外方の、ボンディングしたワイヤ4から見て次にボンディングする電極側するのが好ましい。
【0021】
また半導体素子3”が、図4(a)に示すような上面中央部に長方形の凹部32が形成されたものである場合、キャピラリ5のフェイス面51で突起6を押しつぶすときには、同図(b)に示すように、キャピラリ5を半導体素子3”の内方に移動させ、キャピラリ5の先端に形成されている金属ボールbが前記凹部32に入るようにするのが好ましい。このようにキャピラリ5を移動制御することにより、金属ボールbが半導体素子3”およびボンディングされたワイヤと接触せず、またキャピラリのフェイス面の径をできるだけ小さくすることができる。
【0022】
【発明の効果】
本発明のワイヤボンディング方法では、第2電極のスティッチボンディングした部分に重ねてボールボンディングを行うと共に、キャピラリ先端部のフェイス面の半径を、半導体素子の上面外周辺から第2電極のボールボンディング跡の中心までの最短距離よりも長くするとともに、フェイス面に15°以下の傾斜をもたせ、第2電極のボールボンディング跡に形成される突起を、前記フェイス面で押しつぶすので、ワイヤを第2電極に強力に固着できると同時に半導体装置の薄型化が図れる。
【0023】
また、新たな設備や工程を導入することなく、キャピラリの移動制御を変更するだけで突起をなくすことができるので、経済的で生産性の低下も抑えられる。
【図面の簡単な説明】
【図1】 本発明のワイヤボンディング方法の一例を示す工程図の一部である。
【図2】 図1のワイヤボンディング方法を示す工程図の続きである。
【図3】 上面に複数の電極が形成された半導体素子におけるワイヤボンディング方法の一例を示す概説図である。
【図4】 上面に複数の電極が形成された他の半導体素子におけるワイヤボンディング方法の一例を示す概説図である。
【図5】 従来のワイヤボンディング方法の一例を示す断面図である。
【図6】 従来のワイヤボンディング方法の他の例を示す断面図である。
【図7】 従来のキャピラリのフェイス面の大きさと、半導体素子の幅との関係を示す概説図である。
【図8】 本発明における「最短距離」を示す説明図である。
【符号の説明】
1 回路基板
2 第1電極
3,3’,3” 半導体素子
4 ワイヤ
5 キャピラリ
6 突起
b 金属ボール
B1,B2 ボールボンディング部
S スティッチボンディング部
31 上面電極(第2電極)
51 フェイス面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wire bonding method for connecting electrodes with wires, and more particularly, to a wire bonding method for reinforcing adhesion between a wire and an electrode by performing ball bonding on a stitch bonded portion.
[0002]
[Prior art]
In recent years, various attempts have been made to reduce the thickness of semiconductor devices including semiconductor light emitting devices. As one of the methods, when the
[0003]
On the other hand, although this wire bonding method has no directivity in bonding and excellent workability, the stitch bonding portion S has a smaller crimping area than the ball bonding portion B and the thickness of the crimping portion is thin, so that the bonding strength There was an essential problem that was weak. According to the experience of the present inventor, the reason has not been clarified yet, but when the wire is stitch bonded to the upper surface electrode of the semiconductor element, there is a problem that the wire is particularly easily cut.
[0004]
Therefore, for the purpose of increasing the fixing strength of the stitch bonding portion S, it has been proposed to perform ball bonding overlapping the stitch bonding portion S (for example, Reference 2).
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-15542 (claim column, FIG. 2)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 11-163026 (column of claims, FIG. 2)
[0006]
[Problems to be solved by the invention]
When this method is applied to the wire bonding method shown in FIG. 5, the fixing strength of the wire is surely increased. However, as shown in FIG. 6, a rising portion (projection) 6 of the wire is unavoidable at the ball bonding portion B 2. Therefore, the object of thinning the semiconductor device could not be sufficiently achieved.
[0007]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to strongly fix a wire and an electrode, particularly, a wire and an upper electrode of a semiconductor element, and a semiconductor device. An object of the present invention is to provide a wire bonding method capable of reducing the thickness of the wire.
[0008]
It is another object of the present invention to provide a wire bonding method capable of firmly fixing a wire and an electrode without requiring new equipment and reducing the productivity of the apparatus.
[0009]
[Means for Solving the Problems]
According to the present invention, after the wire is ball-bonded to the first electrode using the capillary, the capillary is placed on the upper surface of the semiconductor element and higher than the first electrode while the wire is drawn out from the capillary. In a wire bonding method in which a wire is bonded to the second electrode after the wire is stitch-bonded to the second electrode and then bonded to the stitch-bonded portion of the second electrode. The radius is made longer than the shortest distance from the outer periphery of the upper surface of the semiconductor element to the center of the ball bonding trace of the second electrode , and the face surface has an inclination of 15 ° or less so that the ball bonding trace of the second electrode is formed. The protrusion formed on the face is crushed by the face surface. Ya bonding method is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In order to increase the fixing strength of the stitch-bonded portion, the inventor performs ball bonding on the stitch-bonded portion in the same manner as in the prior art, and the ball bonding is performed on the second electrode on the premise of this. The problem, that is, whether or not the protrusion formed on the ball bonding trace of the second electrode could be removed was examined. If the protrusions are simply removed, for example, the protrusions can be crushed with a holding jig after the wire bonding process, or the protrusions can be cut with a cutting jig, but new equipment is required to crush or cut the protrusions. In addition, the productivity of the apparatus is reduced. Therefore, as a result of further examination as to whether or not the protrusions can be removed with existing equipment, attention was paid to the capillaries used in the wire bonding process, and it was found that the protrusions could be crushed using the capillaries, and the present invention was made. It was.
[0011]
That is, one of the major features of the wire bonding method of the present invention is that the protrusions are crushed by the face surface of the capillary tip. According to such a configuration, the protrusion can be eliminated simply by changing the movement control of the capillary without introducing new equipment, and a reduction in productivity can be suppressed.
[0012]
Another major feature of the present invention is that the radius of the face of the capillary is made longer than the shortest distance from the outer periphery of the upper surface of the semiconductor element to the center of the ball bonding trace of the second electrode. As shown in FIG. 7, since the face surface 51 ′ of the
[0013]
The capillary used in the present invention has the radius of the face surface, and at the same time , the face surface needs to have an inclination of 15 ° or less from the viewpoint of firmly fixing the wire to the electrode in stitch bonding. This is because if the inclination angle of the face surface is larger than 15 °, the pressing force is not sufficiently applied to the wire through the face surface, and the wire may be insufficiently adhered to the electrode. The tilt angle of the face surface means an angle formed by a plane perpendicular to the axial direction at the capillary tip and the face surface.
[0014]
An example of the wire bonding method of the present invention is shown in FIG. In this embodiment, the wire bonding method in the case of a chip type semiconductor device is described. However, the wire bonding method of the present invention is not limited to the chip type semiconductor device, and a wire bonding method of a conventionally known semiconductor element is used. Can be used.
[0015]
First, a metal ball b is formed at the tip of the
[0016]
Next, once again, a metal ball b is formed at the tip of the
[0017]
After forming a metal ball b for the next wire bonding at the tip of the
[0018]
The movement control of the
[0019]
When there are a plurality of electrodes to be wire-bonded in one semiconductor element, the crushing of the
[0020]
Next, the case where the wire bonding method of the present invention is used for a semiconductor element such as an IC in which a plurality of upper surface electrodes are formed will be described. In the semiconductor device of FIG. 3, as shown in FIG. 3A, a plurality of
[0021]
When the
[0022]
【The invention's effect】
In the wire bonding method of the present invention, ball bonding is performed by superimposing on the stitch-bonded portion of the second electrode, and the radius of the face surface of the capillary tip is set from the outer periphery of the upper surface of the semiconductor element to the ball bonding trace of the second electrode. It is longer than the shortest distance to the center , and the face surface has an inclination of 15 ° or less, and the protrusion formed on the ball bonding trace of the second electrode is crushed by the face surface, so that the wire is strong against the second electrode. At the same time, the semiconductor device can be thinned.
[0023]
In addition, since the protrusion can be eliminated simply by changing the movement control of the capillary without introducing new equipment or processes, it is economical and a decrease in productivity can be suppressed.
[Brief description of the drawings]
FIG. 1 is a part of a process chart showing an example of a wire bonding method of the present invention.
FIG. 2 is a continuation of the process diagram showing the wire bonding method of FIG. 1;
FIG. 3 is a schematic diagram showing an example of a wire bonding method in a semiconductor element having a plurality of electrodes formed on an upper surface.
FIG. 4 is a schematic view showing an example of a wire bonding method in another semiconductor element having a plurality of electrodes formed on the upper surface.
FIG. 5 is a cross-sectional view showing an example of a conventional wire bonding method.
FIG. 6 is a cross-sectional view showing another example of a conventional wire bonding method.
FIG. 7 is a schematic diagram showing the relationship between the size of the face surface of a conventional capillary and the width of a semiconductor element.
FIG. 8 is an explanatory diagram showing a “shortest distance” in the present invention.
[Explanation of symbols]
1
51 Face side
Claims (1)
前記キャピラリ先端部のフェイス面の半径を、前記半導体素子の上面外周辺から前記第2電極のボールボンディング跡の中心までの最短距離よりも長くするとともに、フェイス面に15°以下の傾斜をもたせ、前記第2電極のボールボンディング跡に形成される突起を、前記フェイス面で押しつぶすことを特徴とするワイヤボンディング方法。After the wire is ball-bonded to the first electrode using the capillary, the capillary is placed on the second electrode, which is formed on the upper surface of the semiconductor element and is higher than the first electrode, while feeding the wire from the capillary. In a wire bonding method of moving and stitching a wire to the second electrode and then performing ball bonding on the stitched portion of the second electrode,
The radius of the face surface of the capillary tip is made longer than the shortest distance from the outer periphery of the upper surface of the semiconductor element to the center of the ball bonding trace of the second electrode , and the face surface is inclined by 15 ° or less , A wire bonding method, wherein a protrusion formed on a ball bonding mark of the second electrode is crushed by the face surface.
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US12142595B2 (en) * | 2020-12-23 | 2024-11-12 | Skyworks Solutions, Inc. | Apparatus and methods for tool mark free stitch bonding |
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