JP5017990B2 - Semiconductor device and wiring joining method thereof - Google Patents

Semiconductor device and wiring joining method thereof Download PDF

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JP5017990B2
JP5017990B2 JP2006264733A JP2006264733A JP5017990B2 JP 5017990 B2 JP5017990 B2 JP 5017990B2 JP 2006264733 A JP2006264733 A JP 2006264733A JP 2006264733 A JP2006264733 A JP 2006264733A JP 5017990 B2 JP5017990 B2 JP 5017990B2
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joining
semiconductor chip
metal foil
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wiring
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文達 新野
清治 今村
忠弘 岩倉
慎司 多田
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Fuji Electric Co Ltd
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  • Engineering & Computer Science (AREA)
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  • Pressure Welding/Diffusion-Bonding (AREA)

Description

本発明は、ＩＧＢＴモジュールなどのパワー半導体装置を対象とした配線構造、およびその配線構造に適用する配線接合方法，摩擦攪拌接合装置に関する。   The present invention relates to a wiring structure for a power semiconductor device such as an IGBT module, a wiring bonding method applied to the wiring structure, and a friction stir welding apparatus.

最近では、半導体チップのシュリンク化に伴いパッケージ内部の配線を在来のボンディングワイヤから通電容量，伝熱性の高いリードフレームに変更した配線構造が多く採用されるようになっている。
次に、ＩＧＢＴモジュールを例に、内部配線部材にリードフレームを採用した半導体装置の従来における組立構造を図４に示す。図において、１は放熱用金属ベース、２は絶縁基板（例えばセラミック基板２ａの表裏両面に厚さ0.２〜0.２５mm程度の銅箔を直接接合して導体パターン２ｂ，２ｃを形成したDirect Copper Bonding基板）、３は絶縁基板２の導体パターン２ｂに半田マウントした半導体チップ（ＩＧＢＴ）、３ａは半導体チップ３の電極面にスパッタ成膜した金属膜（アルミ，あるいは半田との濡れ性を高めるようにアルミ膜の表面にＮｉ−Ａｕのメッキを施して形成した厚さ１０μｍ程度の金属膜）、４は半導体チップ３の上面電極(ＩＧＢＴのエミッタ電極)と絶縁基板２の導体パターン２ｂとの間にまたがって半田接合した配線部材としてのリードフレーム、５は絶縁基板２の導体パターン２ｂに接合して外部に引出したリードフレーム（外部導出端子）である。 Recently, with the shrinking of semiconductor chips, a wiring structure in which wiring inside a package is changed from a conventional bonding wire to a lead frame having high current carrying capacity and high heat conductivity has been adopted.
Next, FIG. 4 shows a conventional assembly structure of a semiconductor device employing a lead frame as an internal wiring member, taking an IGBT module as an example. In the figure, 1 is a heat dissipating metal base, 2 is an insulating substrate (for example, a direct conductive pattern 2b, 2c formed by directly bonding a copper foil having a thickness of about 0.2 to 0.25 mm on both front and back surfaces of a ceramic substrate 2a) (Copper Bonding Substrate) 3 is a semiconductor chip (IGBT) mounted by soldering on the conductor pattern 2b of the insulating substrate 2, and 3a is a metal film (aluminum or solder wettability) formed on the electrode surface of the semiconductor chip 3 by sputtering. 4 is a metal film having a thickness of about 10 μm formed by plating Ni—Au on the surface of the aluminum film), and 4 is an upper electrode (IGBT emitter electrode) of the semiconductor chip 3 and a conductor pattern 2b of the insulating substrate 2 A lead frame 5 serving as a wiring member soldered across the lead frame 5 is a lead frame (external lead-out terminal) that is joined to the conductor pattern 2b of the insulating substrate 2 and led out.

ここで、リードフレーム４，５は、半導体素子の電流容量などによって異なるが、一般には幅３mm，厚さ0.５〜1.５mm程度の銅，アルミニウムまたはその合金などで作られた導体片の両端を曲げ加工してＬ字形の接合脚片４ａ，５ａを形成したもので、接合脚片４ａ，５ａを絶縁基板２の導体パターン２ｂ，半導体チップ３の上面側金属膜３ａに重ねてリフロー半田接合している。なお、その半田層を符号６で表す。   Here, the lead frames 4 and 5 differ depending on the current capacity of the semiconductor element, but generally are conductor pieces made of copper, aluminum or an alloy thereof having a width of about 3 mm and a thickness of about 0.5 to 1.5 mm. Both ends are bent to form L-shaped joining leg pieces 4a and 5a. The joining leg pieces 4a and 5a are superposed on the conductor pattern 2b of the insulating substrate 2 and the upper surface side metal film 3a of the semiconductor chip 3, and reflow soldering is performed. It is joined. The solder layer is denoted by reference numeral 6.

ところで、前記のようにリードフレーム４，５を絶縁基板２，半導体チップ３に半田接合した配線構造では、半田接合時の熱履歴により接合界面に金属間化合物が生成し、これが基で接合強度が劣化して接合部の信頼性，寿命が低下する。また、絶縁基板２のセラミック基板２ａ，半導体チップ（Ｓｉ）３とリードフレーム（銅，アルミ材）との線膨張係数差に起因して半田層６の接合界面には、熱サイクルにより繰り返し加わる応力でクラックが発生し、パワーサイクル耐性を低下させるなどの問題もある。   By the way, in the wiring structure in which the lead frames 4 and 5 are solder-bonded to the insulating substrate 2 and the semiconductor chip 3 as described above, an intermetallic compound is generated at the bonding interface due to the thermal history at the time of solder bonding, and based on this, the bonding strength is increased. Deterioration will reduce the reliability and life of the joint. Further, the stress applied repeatedly to the bonding interface of the solder layer 6 due to the thermal cycle due to the difference in linear expansion coefficient between the ceramic substrate 2a of the insulating substrate 2, the semiconductor chip (Si) 3 and the lead frame (copper, aluminum material). There are also problems such as cracking and lowering power cycle resistance.

そこで、昨今では半田を用いない接合方法として、超音波ボンディング法がワイヤボンディング，リードフレーム配線の接合に多く採用されるようになっている。また、最近では少ない熱入力で金属間を固相接合する摩擦攪拌接合法が注目され、この摩擦攪拌接合法を電子回路部品の接合に適用する（例えば、特許文献１参照）研究も進んでいる。
この摩擦攪拌接合法は、２枚の被接合金属板を突き合わせるか、あるいは重ね合わせた上で、その接合部に高速回転するピン状の回転ツール（工具と同様な超硬合金製）を押し込み、その回転により発生する摩擦熱で金属材を軟化，塑性流動させて被接合金属板を固相接合する方法であり、一般の構造物のほかに電子部品に用いる薄板（板厚0.２mm）のアルミ材を重ね合わせて回転ツールにより接合するマイクロスポット摩擦攪拌接合法の実験例も報告されている(非特許文献１参照)。
特開２００３−２５０７８号公報（第１−２頁） 吉川 勝幸，「マイクロスポット摩擦攪拌接合」，(社)溶接学会マイクロ接合研究委員会，第11回エレクトロニクスにおけるマイクロ接合・実装技術シンポジウム論文集, 2005, p421-424 Therefore, in recent years, as a bonding method that does not use solder, an ultrasonic bonding method is often employed for bonding wire bonding and lead frame wiring. Recently, a friction stir welding method in which solid-phase joining between metals is performed with a small amount of heat input has attracted attention, and research on applying this friction stir welding method to the joining of electronic circuit components (for example, see Patent Document 1) is also progressing. .
In this friction stir welding method, two metal plates to be joined are abutted or overlapped, and then a pin-shaped rotating tool (made of cemented carbide similar to a tool) is pushed into the joint. In this method, the metal material is softened and plastically flowed by frictional heat generated by the rotation, and the metal plates to be joined are solid-phase joined. In addition to general structures, a thin plate (0.2 mm thick) used for electronic components An experimental example of a microspot friction stir welding method in which aluminum materials are superposed and joined with a rotating tool has also been reported (see Non-Patent Document 1).
JP 2003-25078 A (page 1-2) Yoshikawa Katsuyuki, “Microspot Friction Stir Welding”, Japan Welding Society Microjoining Research Committee, Proceedings of the 11th Symposium on Microjoining and Mounting Technology in Electronics, 2005, p421-424

そこで、発明者等は前記のマイクロスポット摩擦攪拌接合法を図４の半導体装置に適用し、そのリードフレームを半導体チップの上面に摩擦攪拌接合する方法について実験，検証を試みた。図５は発明者等が行った実験による接合部の模式図であり、ここで回転ツール７として、大径なショルダーの先端に小径なピン７ｂを形成したものを用いた。そして、図示のように半導体チップ３の上面電極に成層した金属膜３ａにリードフレーム配線４の接合脚片４ａ重ね合わせた上で、上方から高速回転している回転ツール７を接合脚片４ａに押し込んで複数地点をスポット接合した。   Therefore, the inventors applied the above-described micro spot friction stir welding method to the semiconductor device of FIG. 4 and tried to test and verify a method of friction stir welding the lead frame to the upper surface of the semiconductor chip. FIG. 5 is a schematic view of a joint portion obtained by an experiment conducted by the inventors. Here, a rotating tool 7 having a small-diameter pin 7b formed at the tip of a large-diameter shoulder is used. Then, as shown in the figure, the joint tool 4a of the lead frame wiring 4 is superimposed on the metal film 3a formed on the upper surface electrode of the semiconductor chip 3, and the rotating tool 7 rotating at high speed from above is applied to the joint leg 4a. It was pressed and spot-bonded at multiple points.

上記のように回転ツール７に加圧力Ｆを加えながら接合脚片４ａの上に押し込むと、回転ツール７の回転による摩擦熱でツール周辺の接合部材が軟化、塑性流動して攪拌され、その後に回転ツール７を引き上げるとリードフレーム配線４の接合脚片４ａと接合金属膜３ａとの間がスポット接合（固相接合）される。なお、図中では接合脚片４ａの厚さをｔ１，半導体チップ３の上面に成膜した金属膜３ａの膜厚ｔ２、摩擦攪拌接合部を符号８で表している。   As described above, when the rotary tool 7 is pushed onto the joint leg piece 4a while applying the pressing force F, the joint member around the tool is softened by the frictional heat generated by the rotation of the rotary tool 7 and is plastically flowed and stirred. When the rotary tool 7 is pulled up, the joining leg piece 4a of the lead frame wiring 4 and the joining metal film 3a are spot joined (solid phase joining). In the figure, the thickness of the joining leg piece 4a is indicated by t1, the thickness t2 of the metal film 3a formed on the upper surface of the semiconductor chip 3, and the friction stir welding portion is indicated by reference numeral 8.

ところで、前記した摩擦攪拌接合の実験，考察を通じて得た知見から、半導体装置の配線構造に適用するマイクロ摩擦攪拌接合の実用化には次記のような課題のあることが判った。すなわち、
（１）半導体装置に組み込むリードフレーム４，５の両端に形成した接合脚片４ａ，５ａの外形は高々□３mm程度であり、この脚片の微小面積に回転ツールを押し込んで絶縁基板２の導電パターン２ｂ，半導体チップ３の電極面に成膜した金属膜３ａに複数地点でスポット接合するには、回転ツール７の先端径を細くする必要がある。しかしながら、先端径の細い回転ツール７では接合部に生じる発熱量が少なく、在来品と同様に板厚ｔ１が０.５〜１.５mmである単体部品のリードフレームでは接合部材の塑性流動化が十分進まずに高信頼性の接合強度を確保するのが困難である。
（２）また、接合界面における塑性流動範囲を拡大するために、回転ツール７に加える加圧力Ｆを高めて先端のピン７ａがリードフレーム４の接合脚片を貫通して接合相手部材の領域まで達するように深く押し込むようにすると、特に半導体チップ３に対しては、高速回転する回転ツールがチップ表面に成膜した金属膜（厚さｔ２が１０μｍ程度）を突き破って半導体チップ３の電極面を損傷するほか、回転ツールに加える加圧力の集中荷重でチップ割れを引き起こすダメージの危険がある。
（３）さらに、摩擦攪拌接合の工程で回転ツールを押し当てた際に、絶縁基板，半導体チップの上に重ね合わせたリードフレームの接合脚片が連れ回りしないように接合位置に固定しておく必要があるが、半導体装置の組立構造は絶縁基板上に回路部品が高密度で実装されていることから、単純に二枚の金属板を裸の状態で接合する場合とは異なり、クリップなどの固定治具でリードフレームの接合脚片を接合位置に固定することは実際には困難である。
（４）そのほか、半導体チップ／リードフレーム間の接合部には導体チップ（Ｓｉ）とリードフレーム（Ｃｕ，Ａｌ）との線膨張係数差が原因で接合部に熱応力が作用する。この場合に、半田接合では半導体チップ，リードフレームに比べてヤング率の低い半田層が熱膨張差に起因する熱応力を吸収するが、接合摩擦攪拌接合法により線膨張率の小さな半導体チップと引っ張り剛性，曲げ剛性の大きなリードフレームとの間を複数箇所でスポット接合した構造では、半田層のような緩衝層がないために熱膨張差に起因する熱応力がスポット接合部に直接作用し、このままではスポット状の接合部が剥がれるなどの破損が生じてリードフレームの通電，放熱機能がダメージを受けるほか、半導体チップの電極面も破壊されるおそれがある。 By the way, based on the knowledge obtained through the above-described experiments and considerations of friction stir welding, it has been found that there is the following problem in the practical use of micro friction stir welding applied to the wiring structure of a semiconductor device. That is,
(1) The outer shape of the joining leg pieces 4a and 5a formed at both ends of the lead frames 4 and 5 incorporated in the semiconductor device is at most about □ 3 mm. The rotating tool is pushed into the minute area of the leg piece to conduct the insulating substrate 2 In order to spot-bond the pattern 2b and the metal film 3a formed on the electrode surface of the semiconductor chip 3 at a plurality of points, it is necessary to reduce the tip diameter of the rotary tool 7. However, with the rotary tool 7 with a small tip diameter, the amount of heat generated at the joint is small, and as with conventional products, in the lead frame of a single part with a plate thickness t1 of 0.5 to 1.5 mm, the plastic fluidization of the joint member is achieved. However, it is difficult to secure a highly reliable joint strength without sufficiently progressing.
(2) Further, in order to expand the plastic flow range at the joining interface, the pressure F applied to the rotary tool 7 is increased so that the pin 7a at the tip penetrates the joining leg piece of the lead frame 4 to the region of the joining partner member. When the semiconductor chip 3 is pushed in deeply, the rotating tool that rotates at high speed breaks through the metal film (thickness t2 is about 10 μm) formed on the chip surface, and the electrode surface of the semiconductor chip 3 is formed. In addition to damage, there is a risk of damage that causes chip cracking due to the concentrated load of pressure applied to the rotating tool.
(3) Further, when the rotary tool is pressed in the friction stir welding process, the lead frame joining leg pieces superimposed on the insulating substrate and the semiconductor chip are fixed at the joining position so that they do not rotate. Although it is necessary, the assembly structure of a semiconductor device has circuit components mounted on an insulating substrate at a high density, so it is different from simply joining two metal plates in a bare state. In practice, it is difficult to fix the joining leg piece of the lead frame at the joining position with the fixing jig.
(4) In addition, thermal stress acts on the joint between the semiconductor chip and the lead frame due to the difference in linear expansion coefficient between the conductor chip (Si) and the lead frame (Cu, Al). In this case, the solder layer having a lower Young's modulus than the semiconductor chip or lead frame absorbs the thermal stress due to the difference in thermal expansion in solder bonding, but it is pulled with the semiconductor chip having a low linear expansion coefficient by the bonding friction stir welding method. In a structure where spot bonding is performed at multiple locations between a lead frame with high rigidity and bending rigidity, there is no buffer layer such as a solder layer, so the thermal stress due to the difference in thermal expansion acts directly on the spot bonding portion and remains as it is. In such a case, damage such as peeling off of the spot-like joint portion may occur, which may damage the energization and heat dissipation function of the lead frame, and may also destroy the electrode surface of the semiconductor chip.

本発明は上記の点に鑑みなされたものであり、スポット摩擦攪拌接合法を適用して半導体チップの上面主電極に配線部材（リードフレーム）を接合した半導体装置を対象に、先記実験の考察結果を基に配線部材として使用するリードフレームを見直し、高い通電容量，放熱性の確保と併せて、半導体チップに不当な荷重を加えずに配線部材を接合して信頼性の高い接合強度が得られるように改良した半導体装置の配線構造、およびその配線構造に適用する配線接合方法，摩擦攪拌接合装置を提供することを目的とする。   The present invention has been made in view of the above points, and considers the above-mentioned experiment for a semiconductor device in which a spot friction stir welding method is applied and a wiring member (lead frame) is bonded to an upper surface main electrode of a semiconductor chip. Based on the results, the lead frame used as a wiring member was reviewed, and in addition to ensuring high current carrying capacity and heat dissipation, the wiring member was joined without applying an undue load to the semiconductor chip, resulting in a highly reliable joint strength. An object of the present invention is to provide a wiring structure of a semiconductor device improved as described above, a wiring joining method applied to the wiring structure, and a friction stir welding apparatus.

上記目的を達成するために、本発明によれば、絶縁基板にマウントした半導体チップの上面主電極と絶縁基板の導体パターンとの間に配線部材を布設し、その両端を相手部材に重ね接合した半導体装置において、
前記配線部材として、１枚の厚さが１０〜１００μｍであるリボン状金属箔の複数枚を組にして用い、半導体チップ／配線部材間の接合部では前記金属箔の接合代を一枚ずつ前後にずらして半導体チップの電極面に成層した金属膜の上に重ね、この位置で各枚ごとに金属箔の接合代と半導体チップの金属膜との間を複数地点でスポット状に摩擦攪拌接合するものとし（請求項１）、好ましくは前記金属箔の接合代の一部を隣接する金属箔の接合端部に重ねて接合するようにする（請求項２）。 In order to achieve the above object, according to the present invention, a wiring member is laid between the upper surface main electrode of a semiconductor chip mounted on an insulating substrate and a conductor pattern of the insulating substrate, and both ends thereof are overlapped and bonded to a mating member. In semiconductor devices,
As the wiring member, a plurality of ribbon-like metal foils each having a thickness of 10 to 100 μm are used as a set, and at the junction between the semiconductor chip and the wiring member, the metal foil joining margin is about one by one. And overlaid on the metal film layered on the electrode surface of the semiconductor chip, and at this position, the friction stir welding is performed at multiple points in a spot shape between the metal foil bonding margin and the metal film of the semiconductor chip. (Claim 1) Preferably, a part of the joining margin of the metal foil is overlapped and joined to the joining end of the adjacent metal foil (Claim 2).

一方、本発明によれば、絶縁基板にマウントした半導体チップの上面主電極と絶縁基板の導体パターンとの間に配線部材を布設し、その両端を相手部材に重ね接合する半導体装置の配線接合方法であって、前記配線部材として、１枚の厚さが１０〜１００μｍであるリボン状金属箔の複数枚を組にして用い、半導体チップ／配線部材間の接合部では前記金属箔の接合代を一枚ずつ前後にずらして半導体チップの電極面に成層した金属膜の上に重ね、相手部材の上に重ね合わせた金属箔の接合代をその接合位置から動かないように押え込み保持し、この状態で上方から回転ツールを接合代に押し込んで各枚ごとに金属箔の接合代と半導体チップの金属膜との間を複数地点でスポット状に摩擦攪拌接合するようにし（請求項３）、また、金属箔と接合相手部材との線膨張係数差によりスポット接合部に作用する熱応力を低減策として、金属箔の接合代に対して最初の地点をスポット接合した後、次のスポット接合地点との間で接合代をアーチ状に撓ませた上で次の地点に回転ツールを押し込んでスポット接合するようにする（請求項４）。 On the other hand, according to the present invention, a wiring bonding method for a semiconductor device, in which a wiring member is laid between a top main electrode of a semiconductor chip mounted on an insulating substrate and a conductor pattern of the insulating substrate, and both ends thereof are overlapped and bonded to a mating member. In this case, as the wiring member, a plurality of ribbon-shaped metal foils each having a thickness of 10 to 100 μm are used as a set, and the joining margin of the metal foil is used at the junction between the semiconductor chip and the wiring member. Move the metal foil layered on the electrode surface of the semiconductor chip one by one and move it back and forth, and hold the metal foil stacked on the mating member in place so that it does not move from its bonding position. Then, the rotary tool is pushed into the joining allowance from above, and the friction stir welding is performed in a spot form at a plurality of points between the joining allowance of the metal foil and the metal film of the semiconductor chip for each sheet (Claim 3), Metal foil and As a measure to reduce the thermal stress acting on the spot joint due to the difference in coefficient of linear expansion from the mating member, after joining the first spot with respect to the joining margin of the metal foil, joining with the next spot joining point After bending the allowance into an arch shape, the rotary tool is pushed into the next point to perform spot joining.

さらに、前記の配線接合方法に適用する本発明の摩擦攪拌接合装置は、縦送り，横送り可能な移動テーブル機構に搭載して駆動主軸に連結した回転ツールと、回転ツールを挟んでその左右に配し、かつ押しばねを介して前記移動テーブルに吊り下げ支持した一対の押えアームと、該アームの先端に連結して金属箔の接合代をスポット接合位置に保持する押さえ込みヘッドを具備した構成とし、具体的には押え込みヘッドを次記のような態様で構成する。
（１）押え込みヘッドは、押えアームの先端に跨がって首振り自在に軸支連結するとともに、該ヘッドの中央に回転ツールの通し穴を開口する。
（２）前項（１）において、押え込みヘッドの下面を凹凸状に粗面化（表面にローレット目を形成）するか、もしくはゴムなどの摩擦係数が大きいスリップ防止層を成層する。 Further, the friction stir welding apparatus of the present invention applied to the above-described wiring joining method includes a rotary tool mounted on a movable table mechanism capable of vertical feed and lateral feed and connected to a drive spindle, and a left and right side of the rotary tool. arranged, and press and a pair of presser arms suspended and supported on the moving table via a spring, a structure in which the bonding margins of the metal foil is connected to the distal end of the arm comprises a hold-down head to hold the spot joining position the specifically hold-down head configured in such a manner the following SL.
(1) The presser head is pivotally coupled so as to swing freely across the tip of the presser arm, and a through hole of the rotary tool is opened at the center of the head .
(2) In the above item (1), the lower surface of the pressing head is roughened (formed with knurled eyes on the surface), or an anti-slip layer having a large friction coefficient such as rubber is formed .

上記した半導体装置の配線構造，およびその配線構造に適用する配線接合方法によれば、配線部材（リードフレーム）として、１枚の厚さが薄いリボン状金属箔の複数枚を組にして用い、半導体チップに対しては金属箔の接合代を一枚ずつ前後にずらして半導体チップの電極面に成層した金属膜の上に重ねて摩擦攪拌接合法でスポット接合したことにより、複数枚の金属箔で必要な通電容量と放熱性を確保しつつ、回転ツールを押し込む摩擦攪拌接合工程では半導体チップにダメージを与えるおそれなしに信頼性の高い接合が実現できる。   According to the wiring structure of the semiconductor device and the wiring bonding method applied to the wiring structure, a plurality of ribbon-shaped metal foils each having a small thickness are used as a wiring member (lead frame). For semiconductor chips, the metal foil bonding margins are shifted one by one back and forth, and are superimposed on the metal film layered on the electrode surface of the semiconductor chip and spot-bonded by the friction stir welding method. In the friction stir welding process in which the rotating tool is pushed in while ensuring the necessary current carrying capacity and heat dissipation, it is possible to achieve highly reliable bonding without fear of damaging the semiconductor chip.

また、金属箔はその接合代の一部を隣接する金属箔の接合端部に重ねて接合するようにすることにより、面積の限られた半導体チップの上面電極面に複数枚の金属箔をスペース効率よく布設接合できるほか、この接合代の重なり部分に回転ツールに加える加圧力を分散させ、半導体チップへの集中荷重を避けて安全に接合が行える。
さらに、金属箔の接合代に対して複数地点をスポット接合する際に、最初の地点をスポット接合した後、次のスポット接合地点との間で接合代をアーチ状に撓ませた上で次の地点に回転ツールを押し込んでスポット接合するようにすることで、半導体チップ／金属箔の熱膨張差に起因してスポット接合地点の間に作用する熱応力を前記アーチ形状の変形により効果的に吸収緩和することができて接合部破損を防止できる。 In addition, a part of the metal foil is overlapped and joined to the joint end part of the adjacent metal foil, so that a plurality of metal foils are spaced on the upper electrode surface of the semiconductor chip having a limited area. In addition to efficient laying and joining, the pressure applied to the rotating tool can be dispersed in the overlapping part of the joining allowance, and safe joining can be performed while avoiding concentrated loads on the semiconductor chip.
Furthermore, when spot-joining a plurality of points with respect to the joining margin of the metal foil, after spot joining the first spot, the joining margin is bent in an arch shape with the next spot joining spot, and then the next spot is joined. By inserting a rotary tool into the spot and performing spot bonding, the thermal stress acting between the spot bonding points due to the difference in thermal expansion of the semiconductor chip / metal foil is effectively absorbed by the deformation of the arch shape. It can be mitigated and joint damage can be prevented.

一方、前記した配線接合方法の実施に適用する本発明の摩擦攪拌接合装置では、回転ツールに併設して金属箔の接合代を接合位置に押さえ込む機構を設けたことにより、半導体装置の組立構造に制約されることなく配線部材の摩擦攪拌接合を作業能率よく行うことができる。また、その接合工程で移動テーブル機構の横送り機能を活用することで、金属箔の接合代にスポット接合地点間の熱応力吸収部として機能するアーチ形状を形成させることができる。   On the other hand, in the friction stir welding apparatus of the present invention applied to the implementation of the above-described wiring bonding method, a mechanism for pressing the metal foil bonding allowance to the bonding position is provided in addition to the rotary tool, so that the assembly structure of the semiconductor device is achieved. Friction stir welding of the wiring members can be performed efficiently without restriction. Further, by utilizing the lateral feed function of the moving table mechanism in the joining process, it is possible to form an arch shape that functions as a thermal stress absorbing portion between spot joining points in the joining margin of the metal foil.

以下、本発明の実施の形態を図１〜図３に示す実施例に基づいて説明する。なお、図１は半導体チップに対する配線構造を表す図、図２は図１の配線構造に適用する摩擦攪拌接合装置の構成図、図３は図２の摩擦攪拌接合装置による接合工程の説明図であり、実施例の図中で図４，図５に対応する部材には同じ符号を付してその詳細な説明は省略する。
まず、図１（ａ），（ｂ）において、９は銅，アルミニウムまたはその合金で作られた厚さ１０〜１００μｍのリボン状金属箔で、複数枚の金属箔９を組とする配線部材（リードフレーム）４を半導体チップ３の上面主電極と絶縁基板の導体パターン（図４参照）との間に布設し、以下に述べる摩擦攪拌接合法により各枚の金属箔９を相手部材に接合している。 DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on the examples shown in FIGS. 1 is a diagram showing a wiring structure for a semiconductor chip, FIG. 2 is a configuration diagram of a friction stir welding apparatus applied to the wiring structure of FIG. 1, and FIG. 3 is an explanatory diagram of a joining process by the friction stir welding apparatus of FIG. In the drawings of the embodiment, members corresponding to those in FIGS. 4 and 5 are denoted by the same reference numerals, and detailed description thereof is omitted.
First, in FIGS. 1A and 1B, 9 is a ribbon-like metal foil having a thickness of 10 to 100 μm made of copper, aluminum, or an alloy thereof, and a wiring member (set of a plurality of metal foils 9). A lead frame 4 is laid between the upper main electrode of the semiconductor chip 3 and the conductor pattern of the insulating substrate (see FIG. 4), and each sheet of metal foil 9 is bonded to the mating member by the friction stir welding method described below. ing.

すなわち、前記金属箔９はその端部をＬ形に折り曲げて接合代９ａ（接合代の幅：ｄ）を形成し、半導体チップ３に対しては金属箔９の接合代９ａを図示のように１枚ずつ前後にずらして半導体チップ３の上面電極に成膜した金属膜３ａの上に重ね合わせ、この位置で接合代９ａの各枚ごとに図５で述べた回転ツール７を上方から押し込んで金属膜３ａとの間をスポット接合しており、図示例では３箇所をスポット接合してその接合地点をＳ１〜Ｓ３で示す。また、その接合手順は最初に図示の右端に並ぶ１枚の金属箔９を所定位置に重ね合わせて摩擦攪拌接合によりスポット接合する。次に２枚目の金属箔を１枚目の金属箔からずらした位置に並べ、その接合代９ａの一部（Δｄ）が既に接合されている金属箔の接合代９ａの上に重なるように配置してスポット接合する。以下、同様な手順により残る金属箔９の接合代９ａをスポット接合する。   That is, the end portion of the metal foil 9 is bent into an L shape to form a joining allowance 9a (joining allowance width: d). For the semiconductor chip 3, the joining allowance 9a of the metal foil 9 is as shown in the figure. One by one is shifted back and forth and superimposed on the metal film 3a formed on the upper electrode of the semiconductor chip 3, and at this position, the rotary tool 7 described in FIG. The metal film 3a is spot-bonded. In the illustrated example, three spots are spot-bonded, and the bonding points are denoted by S1 to S3. In the joining procedure, first, a single metal foil 9 arranged on the right end of the figure is overlapped at a predetermined position and spot-welded by friction stir welding. Next, the second metal foil is arranged at a position shifted from the first metal foil so that a part (Δd) of the joining margin 9a overlaps the joining margin 9a of the already joined metal foil. Place and spot join. Hereinafter, the joining margin 9a of the remaining metal foil 9 is spot joined by the same procedure.

上記のように、配線部材４を複数枚の薄い金属箔９に分けた上で、各枚ごとに金属箔９の接合代９ａを前後にずらすように配列して半導体チップ３の上面電極に成層した金属膜３ａの上にスポット摩擦攪拌接合した配線構造とすることにより、複数枚の金属箔９を通電，伝熱路として半導体装置に必要な通電容量，放熱性を確保できる。また、図示例のように隣合う金属箔９の間で接合代９ａの一部を互いに重ねるように配列することで、限られた半導体チップ上の接合面域に接合する金属箔の枚数を増やして通電容量を高めることができる。   As described above, after the wiring member 4 is divided into a plurality of thin metal foils 9, the joining margins 9 a of the metal foils 9 are arranged so as to be shifted back and forth for each sheet and layered on the upper surface electrode of the semiconductor chip 3. By using a wiring structure in which spot friction stir welding is performed on the metal film 3a, the current carrying capacity and heat dissipation required for the semiconductor device can be ensured by using a plurality of metal foils 9 as current conducting and heat transfer paths. Further, as shown in the illustrated example, by arranging a part of the joining allowance 9a so as to overlap each other between adjacent metal foils 9, the number of metal foils to be joined to a joining surface area on a limited semiconductor chip is increased. The energizing capacity can be increased.

また、配線部材４として前記の金属箔９を用いることにより、板厚が厚い単一部品のリードフレーム（図４参照）を半導体チップ３の上面に重ねて摩擦攪拌接合する場合と比べて、回転ツール７に加える加圧力Ｆ（図５参照）を低く抑えて半導体チップ３に過度な押圧荷重を加えることなしに接合が行える。さらに、金属箔９の引っ張り，曲げ剛性は単一部品のリードフレームと比べて小さく、半導体チップ３との線膨張係数差に起因してスポット接合部に作用する熱応力を金属箔９の変形で吸収緩和することができる。   Further, by using the metal foil 9 as the wiring member 4, the lead frame (see FIG. 4) having a large thickness is overlapped on the upper surface of the semiconductor chip 3 and compared with the case of friction stir welding. Bonding can be performed without applying an excessive pressing load to the semiconductor chip 3 while keeping the pressure F (see FIG. 5) applied to the tool 7 low. Furthermore, the tensile and bending rigidity of the metal foil 9 is smaller than that of a single component lead frame, and the thermal stress acting on the spot joint due to the difference in the linear expansion coefficient with the semiconductor chip 3 is caused by the deformation of the metal foil 9. Absorption can be relaxed.

なお、金属箔９の他端は図４で述べたように絶縁基板２の導体パターンに接合されるが、この導体パターンとの間の接合には必ずしも図１のように金属箔９を各枚ごとに分けて相手部材に摩擦攪拌接合する必要はなく、例えば複数枚の金属箔の接合代を束状に重ね合わせたまま一括して導体パターンに摩擦攪拌接合するようにしてもよい。すなわち、絶縁基板２のセラミック基板２ａは半導体チップ３と比べて堅牢であり、導体パターン２ｂの金属箔厚さ（約０．２５mm）は半導体チップ３の電極面に成層した金属膜３ａ（約１０μｍ）と比べて厚い。したがって、回転ツール７に大きな加圧力Ｆ（図５参照）を加えても問題なく複数枚の金属箔９を一括して絶縁基板２の導体パターンに摩擦攪拌接合することが可能である。また、図４における外部端子のリードフレーム５についても、前記と同様な理由から板厚の厚い単一部品のリードフレームをそのまま採用して摩擦攪拌接合することが可能である。   The other end of the metal foil 9 is joined to the conductor pattern of the insulating substrate 2 as described with reference to FIG. 4, but the metal foil 9 is not necessarily attached to the conductor pattern as shown in FIG. There is no need to perform friction stir welding on the mating member separately for each case, and for example, friction stir welding may be performed on the conductor pattern in a lump while overlapping the joining margins of a plurality of metal foils in a bundle. That is, the ceramic substrate 2 a of the insulating substrate 2 is more robust than the semiconductor chip 3, and the metal foil thickness (about 0.25 mm) of the conductor pattern 2 b is the metal film 3 a (about 10 μm) formed on the electrode surface of the semiconductor chip 3. Is thicker than Therefore, even if a large pressing force F (see FIG. 5) is applied to the rotary tool 7, a plurality of metal foils 9 can be collectively friction-stir welded to the conductor pattern of the insulating substrate 2 without any problem. Also, the lead frame 5 of the external terminal in FIG. 4 can be friction stir welded by directly adopting a single component lead frame having a large plate thickness for the same reason as described above.

次に、前記した配線構造に適用して金属箔９を相手部材に接合する摩擦攪拌接合装置（製造装置）の構成を図２に示す。図２（ａ），（ｂ）において、１０は回転ツール７および後記の金属箔押え込み機構を搭載した縦送り，横送りが可能な移動テーブル機構であり、回転ツール７は移動テーブル機構１０に軸受支持した上で駆動源１１の主軸に連結している。また、金属箔押え込み機構は回転ツール７を挟んでその左右両側に並ぶ一対の押えアーム１２と、押えアーム１２の先端に連結した押え込みヘッド１３との組立体になり、前記押えアーム１２は押しばね（圧縮コイルばね）１４を介して移動テーブル機構１０に吊り下げ支持されている。   Next, FIG. 2 shows a configuration of a friction stir welding apparatus (manufacturing apparatus) that is applied to the above-described wiring structure and joins the metal foil 9 to the mating member. 2 (a) and 2 (b), reference numeral 10 denotes a moving table mechanism capable of vertical feed and lateral feed equipped with a rotary tool 7 and a metal foil pressing mechanism described later. It is connected to the main shaft of the drive source 11 after being supported. The metal foil pressing mechanism is an assembly of a pair of pressing arms 12 arranged on both the left and right sides of the rotary tool 7 and a pressing head 13 connected to the tip of the pressing arm 12, and the pressing arm 12 is a pressing spring. It is suspended and supported by the moving table mechanism 10 via a (compression coil spring) 14.

ここで、押え込みヘッド１３は、後述のように摩擦攪拌接合工程で金属箔９を接合位置から動かないように押さえ込む治具の役目を果たすものであり、その左右両端が支軸１３ａを介して押えアーム１２の間に跨がって首振り自在に連結支持されており、ヘッドの中央には回転ツール４の通し穴１３ｂが開口している。また、図示してないが、押え込みヘッド１３の下面には、例えばローレット目を形成するなどして凹凸面状に粗面化しておくか、あるいはゴムなどの摩擦係数の大きな材質を成層しておき、金属箔９の接合代９ａを確実に押さえ込むようにしている。   Here, the pressing head 13 serves as a jig for pressing the metal foil 9 so as not to move from the bonding position in the friction stir welding process as will be described later, and the both left and right ends thereof are pressed via the support shaft 13a. The arm 12 is supported in a swingable manner across the arm 12, and a through hole 13b of the rotary tool 4 is opened at the center of the head. Although not shown, the lower surface of the pressing head 13 is roughened to have an uneven surface by, for example, forming knurled eyes, or a material having a large friction coefficient such as rubber is layered. The joining margin 9a of the metal foil 9 is surely pressed down.

次に、上記の摩擦攪拌接合装置を使用して半導体チップ／金属箔間を摩擦攪拌スポット接合する接合工程を図３（ａ）〜（ｄ）により説明する。まず、図３（ａ）のように半導体チップ３の上面に１枚の金属箔９の接合代９ａを所定位置に重ねた状態で、あらかじめ指定した第１の接合地点Ｓ１に向けて前記の移動テーブル機構１０を移動し、Ｐ１位置で移動テーブル機構１０を下降して押え込みヘッド１３により金属箔９の接合代９ａを半導体チップ３の上に押さえ込む。次いで高速回転している回転ツール７を下降してその先端をスポット接合地点Ｓ１に押し込み、接合地点Ｓ１をスポット接合する。   Next, a joining process for joining the semiconductor chip / metal foil with the friction stir spot using the above friction stir welding apparatus will be described with reference to FIGS. First, as shown in FIG. 3A, the above-mentioned movement toward the first joint point S1 designated in advance is performed in a state where the joint margin 9a of one metal foil 9 is overlapped on the upper surface of the semiconductor chip 3 at a predetermined position. The table mechanism 10 is moved, the moving table mechanism 10 is lowered at the position P 1, and the joining margin 9 a of the metal foil 9 is pressed onto the semiconductor chip 3 by the pressing head 13. Next, the rotating tool 7 rotating at a high speed is lowered and the tip thereof is pushed into the spot joining point S1, and the joining point S1 is spot joined.

なお、この場合に金属箔９は押え込みヘッド１３により接合位置に押え込み保持されているので回転ツール７と一緒に連れ回りすることはない。また、押え込みヘッド１３は首振り自在に軸支されており、図１で述べたように金属箔９の接合代９ａの一部を隣接する接合代の上に重ねて段差が生じても、この段差に順応して接合代９ａを確実に押さえ込むことができる。また、回転ツール７の下降に伴い押え込みヘッド１３との当接面に一定以上の押圧力が加わると、移動テーブル機構１０と押えアーム１２との間に介挿した押しばね１４が圧縮して半導体チップ３に過大な荷重が掛かるのを防ぐようにしている。   In this case, since the metal foil 9 is pressed and held at the joining position by the pressing head 13, it does not rotate with the rotary tool 7. Further, the pressing head 13 is pivotally supported so that it can swing freely. Even if a step is generated by overlapping a part of the joining margin 9a of the metal foil 9 on the adjacent joining margin as described in FIG. The joining allowance 9a can be surely pressed down according to the step. Further, when a certain pressing force is applied to the contact surface with the pressing head 13 as the rotary tool 7 is lowered, the pressing spring 14 inserted between the moving table mechanism 10 and the pressing arm 12 is compressed and the semiconductor. The tip 3 is prevented from being overloaded.

そして、第１地点Ｓ１のスポット接合が済むと、図３（ｂ）で示すように移動テーブル機構１０を一旦引き上げて次の第２の接合地点Ｓ２に向けて移動するが、この移動過程では第２の接合地点Ｓ２を通り越した位置Ｐ２まで移動し、この位置で押え込みヘッド１３を下降して金属箔９の接合代９ａを押え込む。続いて接合代９ａを押え込んだまま移動テーブル機構を横送りして第２の接合地点Ｓ２に対応する位置Ｐ３に移動する（図３（ｃ）参照）。これにより、金属箔９の接合代９ａは既にスポット接合済みの接合地点Ｓ１との間の領域が撓んで図示の様なアーチ形状部９ｂが形成される。その後に回転ツール７を下降して接合代９ａに押し込み、第２の接合地点Ｓ２をスポット接合する。   After the spot joining at the first point S1, the moving table mechanism 10 is once lifted and moved toward the next second joining point S2 as shown in FIG. 3B. 2 moves to a position P2 that passes over the joining point S2, and at this position, the pressing head 13 is lowered to hold down the joining margin 9a of the metal foil 9. Subsequently, the moving table mechanism is laterally fed while pressing the joining allowance 9a, and moves to a position P3 corresponding to the second joining point S2 (see FIG. 3C). As a result, a region between the joining margin 9a of the metal foil 9 and the joining point S1 that has already been spot-joined is bent to form an arch-shaped portion 9b as illustrated. Thereafter, the rotary tool 7 is lowered and pushed into the joining allowance 9a to spot-join the second joining point S2.

このように移動テーブル機構１０の横送り機能を利用して金属箔９のスポット接合地点間にアーチ形状部９ｂを形成することにより、線膨張係数の異なる半導体チップ３／金属箔９の間に発生する熱応力を前記のアーチ形状部９ｂの変形で吸収して、スポット接合部に作用する応力を緩和できる。
なお、上記の実施例では、半導体チップ３の上面側電極の金属膜３ａに配線部材として金属箔９の接合代９ａを重ねて摩擦攪拌接合する場合を例に説明したが、半導体チップ３の上面側電極にヒートスプレッダを半田接合した上で、このヒートスプレッダの上面に金属箔９を摩擦攪拌接合するようにすることもできる。 As described above, the arch-shaped portion 9b is formed between the spot joining points of the metal foil 9 by using the lateral feed function of the moving table mechanism 10, thereby generating between the semiconductor chip 3 / metal foil 9 having different linear expansion coefficients. The thermal stress to be absorbed can be absorbed by the deformation of the arch-shaped portion 9b, and the stress acting on the spot joint can be relaxed.
In the above-described embodiment, the case where the joining margin 9a of the metal foil 9 as the wiring member is overlapped on the metal film 3a of the upper surface side electrode of the semiconductor chip 3 and friction stir welding is described as an example. The heat spreader may be soldered to the side electrode, and the metal foil 9 may be friction stir welded to the upper surface of the heat spreader.

本発明実施例の半導体装置における主要部の配線構造およびその摩擦攪拌接合の状態を表す図で、（ａ），（ｂ）はそれぞれ側面図，および平面図FIG. 2 is a diagram illustrating a wiring structure of a main part and a state of friction stir welding in a semiconductor device according to an embodiment of the present invention. 図１の配線構造に適用する摩擦攪拌接合装置の構成図で、（ａ），（ｂ）はそれぞれ正面図，および側面図It is a block diagram of the friction stir welding apparatus applied to the wiring structure of FIG. 1, (a), (b) is a front view and a side view, respectively. 図２の摩擦攪拌接合装置による半導体チップ／金属箔間のスポット接合方法の説明図で、（ａ）〜（ｃ）はその接合方法を工程順に表す模式図It is explanatory drawing of the spot joining method between a semiconductor chip / metal foil with the friction stir welding apparatus of FIG. 2, (a)-(c) is a schematic diagram showing the joining method in process order 配線部材としてリードフレームを相手部材に半田接合した従来における半導体装置の組立構造図Assembly structure diagram of a conventional semiconductor device in which a lead frame as a wiring member is soldered to a mating member 図４における半導体チップ／リードフレーム間を摩擦攪拌接合した状態の接合部を模式的に表した図The figure which represented typically the junction part of the state which carried out friction stir welding between the semiconductor chip / lead frame in FIG.

符号の説明Explanation of symbols

２ 絶縁基板
２ａ セラミック基板
２ｂ 導体パターン
３ 半導体チップ
３ａ 金属膜
４，５ リードフレーム（配線部材）
７ 回転ツール
８ 摩擦攪拌接合部
９ 金属箔
９ａ 接合代
１０ 摩擦攪拌接合装置（製造装置）の移動テーブル機構
１２ 押えアーム
１３ 押え込みヘッド
１３ａ 首振り支軸
１３ｂ ツール通し穴
１４ 押しばね 2 Insulating substrate 2a Ceramic substrate 2b Conductive pattern 3 Semiconductor chip 3a Metal film 4, 5 Lead frame (wiring member)
DESCRIPTION OF SYMBOLS 7 Rotating tool 8 Friction stir welding part 9 Metal foil 9a Joining margin 10 Moving table mechanism 12 of friction stir welding apparatus (manufacturing apparatus) Presser arm 13 Pressing head 13a Swing support shaft 13b Tool through hole 14 Press spring

Claims (4)

絶縁基板にマウントした半導体チップの上面主電極と絶縁基板の導体パターンとの間に配線部材を布設し、その両端を相手部材に重ね接合した半導体装置において、
前記配線部材として、１枚の厚さが１０〜１００μｍであるリボン状金属箔の複数枚を組にして用い、半導体チップ／配線部材間の接合部では前記金属箔の接合代を一枚ずつ前後にずらして半導体チップの電極面に成層した金属膜の上に重ね、各枚ごとに金属箔の接合代と半導体チップの金属膜との間を複数地点でスポット状に摩擦攪拌接合したことを特徴とする半導体装置。 In the semiconductor device in which a wiring member is laid between the upper surface main electrode of the semiconductor chip mounted on the insulating substrate and the conductor pattern of the insulating substrate, and both ends thereof are overlapped and joined to the mating member.
As the wiring member, a plurality of ribbon-like metal foils each having a thickness of 10 to 100 μm are used as a set, and at the junction between the semiconductor chip and the wiring member, the metal foil joining margin is about one by one. It is superimposed on the metal film layered on the electrode surface of the semiconductor chip, and the friction stir welding is performed in a spot shape at multiple points between the metal foil bonding margin and the semiconductor chip metal film for each sheet. A semiconductor device. 請求項１に記載の半導体装置において、金属箔は、その接合代の一部を隣接する金属箔の接合代に重ねて接合したことを特徴とする半導体装置。 2. The semiconductor device according to claim 1, wherein the metal foil is joined by overlapping a part of a joining margin thereof to a joining margin of an adjacent metal foil. 絶縁基板にマウントした半導体チップの上面主電極と絶縁基板の導体パターンとの間に配線部材を布設し、その両端を相手部材に重ね接合する半導体装置の配線接合方法であって、
前記配線部材として、１枚の厚さが１０〜１００μｍであるリボン状金属箔の複数枚を組にして用い、半導体チップ／配線部材間の接合部では前記金属箔の接合代を一枚ずつ前後にずらして半導体チップの電極面に成層した金属膜の上に重ね、相手部材の上に重ね合わせた金属箔の接合代をその接合位置から動かないように押え込み保持し、この状態で上方から回転ツールを接合代に押し込んで各枚ごとに金属箔の接合代と半導体チップの金属膜との間を複数地点でスポット状に摩擦攪拌接合することを特徴とする半導体装置の配線接合方法。 A wiring bonding method of a semiconductor device in which a wiring member is laid between a top surface main electrode of a semiconductor chip mounted on an insulating substrate and a conductive pattern of the insulating substrate, and both ends thereof are overlapped and bonded to a mating member ,
As the wiring member, a plurality of ribbon-like metal foils each having a thickness of 10 to 100 μm are used as a set, and at the junction between the semiconductor chip and the wiring member, the metal foil joining margin is about one by one. The metal foil layered on the electrode surface of the semiconductor chip is placed on the surface of the semiconductor chip, and the metal foil superimposed on the mating member is pressed and held so that it does not move from its position. A wiring joining method for a semiconductor device, characterized in that a tool is pushed into a joining margin, and a friction stir welding is performed in a spot shape at a plurality of points between a joining margin of a metal foil and a metal film of a semiconductor chip for each sheet . 請求項３に記載の配線接合方法において、金属箔の接合代に対して最初の地点をスポット接合した後、次のスポット接合地点との間で接合代をアーチ状に撓ませた上で次の地点に回転ツールを押し込んでスポット接合することを特徴とする半導体装置の配線接合方法。 In the wiring joining method according to claim 3, after spot joining the first spot with respect to the joining margin of the metal foil, the joint margin is bent in an arch shape with the next spot joining spot, and then A wiring bonding method for a semiconductor device, characterized in that a rotary tool is pushed into a spot to perform spot bonding.
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