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JP4586508B2 - Semiconductor device and manufacturing method thereof - Google Patents

Semiconductor device and manufacturing method thereof Download PDF

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Publication number
JP4586508B2
JP4586508B2 JP2004338399A JP2004338399A JP4586508B2 JP 4586508 B2 JP4586508 B2 JP 4586508B2 JP 2004338399 A JP2004338399 A JP 2004338399A JP 2004338399 A JP2004338399 A JP 2004338399A JP 4586508 B2 JP4586508 B2 JP 4586508B2
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JP
Japan
Prior art keywords
metal foil
bonding
heat spreader
ultrasonic
manufacturing
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Expired - Fee Related
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JP2004338399A
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Japanese (ja)
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JP2006135270A (en
Inventor
克彦 吉原
岳志 藤井
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Fuji Electric Co Ltd
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Fuji Electric Systems Co Ltd
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Priority to JP2004338399A priority Critical patent/JP4586508B2/en
Publication of JP2006135270A publication Critical patent/JP2006135270A/en
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Publication of JP4586508B2 publication Critical patent/JP4586508B2/en
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Description

本発明は、電力変換装置などに適用するパワー半導体モジュールを対象とした半導体装置，およびその製造方法に関する。   The present invention relates to a semiconductor device intended for a power semiconductor module applied to a power conversion device and the like, and a manufacturing method thereof.

近年になり、電力変換装置に適用するパワー半導体モジュールの小型化，大電流化が進んでおり、これに伴いパワー半導体モジュールに搭載するパワー半導体デバイス（例えば、ＩＧＢＴ（Insulated Gate Bipolar Transistor）,ＦＷＤ（Free Wheeling Diode））等の半導体チップは高い電流密度で通電使用されることが多いことから、その発熱密度の増加に対する放熱対策が重要課題となっている。
すなわち、ＩＧＢＴ，ＦＷＤなどのパワー半導体デバイスは、半導体チップの接合部温度Ｔjを保証制限（例えば１２５℃）している。これに対して、放熱用金属ベース板に搭載した絶縁基板に半導体チップをマウントした片面冷却方式の半導体パッケージは、半導体チップの上面側がパッケージ内に充填した封止樹脂（例えば、シリコーン系封止樹脂（熱伝導率：０．１〜０．２Ｗ／ｍｋ））で封止されているためにチップの上面側からの放熱は殆ど期待できない。このために半導体チップの小型,大電流化に伴いチップの発熱密度（発熱密度の分布はチップの中央部で高く、周辺では低い）が増大すると、半導体チップの上面電極と接続する配線リードにアルミワイヤ(線径φ３００〜４００μｍ)を使用した配線構造では、チップ表面の温度上昇を低く抑えることが困難であるばかりか、アルミワイヤにワイヤ自身のジュール発熱も加わってワイヤが溶断してしまうおそれもある。 In recent years, power semiconductor modules applied to power converters have been reduced in size and increased in current. Accordingly, power semiconductor devices (for example, IGBTs (Insulated Gate Bipolar Transistors), FWDs) mounted on power semiconductor modules have been developed. Since semiconductor chips such as Free Wheeling Diode)) are often energized and used at a high current density, heat dissipation countermeasures against an increase in the heat generation density are an important issue.
That is, in power semiconductor devices such as IGBT and FWD, the junction temperature Tj of the semiconductor chip is guaranteed limited (for example, 125 ° C.). In contrast, a single-sided cooling type semiconductor package in which a semiconductor chip is mounted on an insulating substrate mounted on a heat radiating metal base plate has a sealing resin (for example, a silicone-based sealing resin) in which the upper surface side of the semiconductor chip is filled in the package. (Thermal conductivity: 0.1 to 0.2 W / mk)), the heat radiation from the upper surface side of the chip is hardly expected. For this reason, when the heat generation density of the chip (the distribution of heat generation density is high at the center of the chip and low at the periphery) increases as the size and current of the semiconductor chip increase, aluminum leads are connected to the upper surface electrode of the semiconductor chip. In a wiring structure using a wire (wire diameter of φ300 to 400 μm), it is difficult to keep the temperature rise on the chip surface low, and the wire itself may be melted due to the Joule heat generation of the wire itself. is there.

一方、前記問題の対策として、半導体チップの上面側に熱拡散部材として熱伝導性の高い金属ブロックになるヒートスプレッダを半田付け，あるいは熱伝導性樹脂の接着剤で伝熱的に接合配置し、このヒートスプレッダを介して半導体チップの中央部に集中する発熱をチップ周域に分散させ、半導体チップの最高温度を下げるようにしたものが知られている（例えば、特許文献１参照）。
次に、ヒートスプレッダとして、銅，アルミなどの伝熱，導電性の高い金属ブロックで作られたヒートスプレッダを半導体チップの上に配置して上面電極（ＩＧＢＴのエミッタ電極）半田接合した上で、該ヒートシンクを利用してその上面に配線リードとしてアルミワイヤをボンディングしたパワー半導体モジュールの従来構造を図８に示す。なお、図示例は２組のＩＧＢＴ（Insulated Gate Bipolar Transistor）およびＦＷＤ（Free Wheeling Diode）をセットにしてパッケージに搭載した２個組のパワー半導体モジュールを示している。 On the other hand, as a countermeasure for the above problem, a heat spreader that becomes a metal block having high heat conductivity as a heat diffusion member is soldered on the upper surface side of the semiconductor chip, or heat transfer resin adhesive is used for heat transfer and bonding. It is known that heat generated in the central portion of a semiconductor chip is dispersed in a chip peripheral region via a heat spreader so as to lower the maximum temperature of the semiconductor chip (see, for example, Patent Document 1).
Next, as a heat spreader, a heat spreader made of a metal block having high heat conductivity and conductivity such as copper and aluminum is disposed on the semiconductor chip and soldered to the upper surface electrode (IGBT emitter electrode). FIG. 8 shows a conventional structure of a power semiconductor module in which an aluminum wire is bonded on the upper surface thereof as a wiring lead. The illustrated example shows two sets of power semiconductor modules in which two sets of IGBTs (Insulated Gate Bipolar Transistors) and FWDs (Free Wheeling Diodes) are mounted in a package.

図８（ａ），（ｂ）において、１は放熱用金属ベース（銅ベース）、２はセラミックス基板２ａの表，裏両面に導体パターン２ｂ，２ｃ，２ｄを形成して金属ベース１の上に搭載した絶縁基板（例えば、Direct Copper Bonding基板）、３は絶縁基板２を金属ベース１に接合した半田層、４はＩＧＢＴ（半導体チップ）、５はＩＧＢＴ４の下面電極（コレクタ電極）を絶縁基板２の導体パターン２ｂ（コレクタパターン）に接合した半田層、６はＩＧＢＴ５に並列接続したＦＷＤ、７はＩＧＢＴ4の上面電極（エミッタ電極）の上面に配したヒートスプレッダ、８はヒートスプレッダ７の下面とＩＧＢＴ４の上面電極面との間を接合した半田層、９は配線リードとしてＩＧＢＴ４およびＦＷＤ６の上面に載置したヒートスプレッダ７と絶縁基板２の導体パターン２ｃ（エミッタパターン）との間に配線して超音波接合したボンディングワイヤ（アルミワイヤ）、１０は絶縁基板２の導体パターンに接合して外部に引出したモジュールの入，出力端子である。なお、図示してないが、前記のモジュール組立体には外囲樹脂ケースを組み付けた上で、該ケース内には封止樹脂が充填されている。
特開２０００−３０７０５８号公報 8 (a) and 8 (b), 1 is a heat radiating metal base (copper base), 2 is a conductive pattern 2b, 2c, 2d formed on the front and back surfaces of the ceramic substrate 2a. Mounted insulating substrate (for example, Direct Copper Bonding substrate), 3 is a solder layer in which the insulating substrate 2 is bonded to the metal base 1, 4 is an IGBT (semiconductor chip), and 5 is a lower surface electrode (collector electrode) of the IGBT 4. A solder layer joined to the conductor pattern 2b (collector pattern), 6 is an FWD connected in parallel to the IGBT 5, 7 is a heat spreader disposed on the upper surface of the upper surface electrode (emitter electrode) of the IGBT 4, and 8 is a lower surface of the heat spreader 7 and the upper surface of the IGBT 4 A solder layer bonded to the electrode surface, 9 is a conductor of the heat spreader 7 placed on the upper surface of the IGBT 4 and FWD 6 as a wiring lead and the insulating substrate 2 Bonding wires (aluminum wires) 10, which are wired and ultrasonically bonded to the pattern 2 c (emitter pattern), are input / output terminals of a module bonded to the conductor pattern of the insulating substrate 2 and drawn to the outside. Although not shown, the module assembly is assembled with an enclosing resin case, and the case is filled with sealing resin.
JP 2000-307058 A

ところで、前記のように半導体チップ(ＩＧＢＴ)の上にヒートスプレッダを半田付けした上で、配線リードにボンディングワイヤを採用してヒートスプレッダの上面に超音波接合した組立構造になる従来のパワー半導体モジュールでは、製造面で次記のような問題がある。
例えば、定格電流１２０ＡのＩＧＢＴに対し、配線リードに線径φ３００μｍのアルミワイヤを用いてアルミワイヤ１本当たりの通電電流を８Ａとすると、ＩＧＢＴからの電流取り出しには１５本のアルミワイヤが必要となる。また、このＩＧＢＴを３個並列接続して定格電流３６０Ａに相当する３相インバータ装置のブリッジ回路を構築すると、Ｕ，Ｖ，Ｗ３相分の上アーム，下アームで合計１８個のＩＧＢＴが必要で、その配線リードにアルミワイヤを採用すると必要なワイヤの本数は１５×１８＝２７０本にもなり、そのワイヤボンディング（超音波接合）に要する工数も非常に多くなって工程のリードタイムが長くなる。 By the way, in the conventional power semiconductor module having an assembly structure in which the heat spreader is soldered on the semiconductor chip (IGBT) as described above and then the bonding wire is adopted as the wiring lead and ultrasonically bonded to the upper surface of the heat spreader. There are the following problems in manufacturing.
For example, for an IGBT with a rated current of 120 A, if an aluminum wire with a wire diameter of φ300 μm is used for the wiring lead and the energizing current per aluminum wire is 8 A, 15 aluminum wires are required to extract current from the IGBT. Become. Moreover, when three IGBTs are connected in parallel to construct a bridge circuit for a three-phase inverter device corresponding to a rated current of 360 A, a total of 18 IGBTs are required for the upper and lower arms for the U, V, and W three phases. If an aluminum wire is used for the wiring lead, the number of wires required is as much as 15 × 18 = 270, and the man-hour required for the wire bonding (ultrasonic bonding) is greatly increased, resulting in a long process lead time. .

一方、半導体チップに接続するリード配線の工数削減，放熱性向上を狙いに、前記のアルミワイヤに替えて半導体チップの上面電極に直接ストラップ状の金属箔を超音波接合してリードフレームとの間に配線した半導体装置が、例えば特開平２００２−３１３８５１号公報などで知られているが、半導体チップの上面電極に半田接合したヒートスプレッダの上面に金属箔を超音波接合することについては開示がない。
本発明は上記の点に鑑みなされたものであり、半導体チップの配線リードとして、配線工数が多く，リードタイムの長いアルミワイヤに替えてストラップ状の金属箔を採用した半導体モジュールを対象に、半導体チップの上面電極に半田接合したヒートスプレッダの上面に前記金属箔を超音波接合した半導体装置を提供し、さらにこの半導体装置について、金属箔の超音波接合時に半導体チップ自身，および半導体チップ／ヒートスプレッダ間の半田接合層にクラックが発生するのを抑止しつつ、ヒートスプレッダ／金属箔の間で電流の取り出しに必要な接続面積を確保して安定よく超音波接合が行えるようにした半導体装置の製造方法を提供することにある。 On the other hand, with the aim of reducing lead wiring man-hours connected to the semiconductor chip and improving heat dissipation, a strap-like metal foil is ultrasonically bonded directly to the upper surface electrode of the semiconductor chip instead of the aluminum wire, and between the lead frame. For example, Japanese Patent Application Laid-Open No. 2002-313851 discloses a semiconductor device wired in the above, but there is no disclosure about ultrasonic bonding of a metal foil to the upper surface of a heat spreader solder-bonded to the upper surface electrode of a semiconductor chip.
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is intended for a semiconductor module that employs a strap-like metal foil instead of an aluminum wire having a large number of wiring steps and a long lead time as a wiring lead of a semiconductor chip. Provided is a semiconductor device in which the metal foil is ultrasonically bonded to the upper surface of a heat spreader that is solder-bonded to the upper electrode of the chip. Further, with respect to this semiconductor device, the semiconductor chip itself and between the semiconductor chip and the heat spreader are ultrasonically bonded to the metal foil. Providing a method for manufacturing a semiconductor device capable of stably performing ultrasonic bonding by securing a connection area necessary for extracting current between heat spreaders / metal foils while suppressing occurrence of cracks in a solder bonding layer There is to do.

上記目的を達成するために、本発明による半導体装置は、絶縁基板の導体パターンにマウントしたパワー半導体チップに対し、該半導体チップの上面に導電性のヒートスプレッダを搭載して半導体チップの主電極面との間を半田接合した上で、ヒートスプレッダの上面に配線リード部材としてストラップ状の金属箔を重ねて超音波接合した構成とし、ここで金属箔／ヒートスプレッダ間の通電路となる接合箇所を金属箔とヒートスプレッダの重なり面域に分散させて超音波接合するものとする（請求項１）。
また、本発明によれば、前記半導体装置の製造工程に次記製造方法を適用し、ヒートスプレッダの上面に金属箔を超音波接合するものとする。すなわち、
（１）第１の方法では、その超音波接合工程に適用する超音波ボンディングツールのヘッド面に突起状のローレットを形成しておき、配線リードの金属箔をヒートスプレッダの上面に接合する際に前記ボンディングツールに形成したローレット面の突起を金属箔の上面に押し当てて超音波接合する（請求項２）。
（２）第２の方法では、ヒートスプレッダの上面に超音波接合する金属箔に対し、あらかじめ指定した接合箇所にヒートスプレッダへ向けて凸となる接合突起を分散してプレス成形しておき、金属箔をヒートスプレッダに接合する際に前記突起をヒートスプレッダの上面に重ねた上で、金属箔の上面に超音波ボンディングツールを押し当てて超音波接合する（請求項３）ようにし、ここで前記の接合突起は、ディンプル形状（請求項４）、あるいはボンディングツールに印加する超音波振動の振幅方向と平行に延在する直線状突起（請求項５）として形成することができる。
（３）また、第３の製造方法では、前記の接合突起を金属箔に形成する替わりに、ヒートスプレッダの上面に分散形成しておき、ヒートスプレッダに金属箔を超音波接合する際にヒートスプレッダに形成した前記接合突起の上に平坦な金属箔を重ねた上で、金属箔の上面に超音波ボンディングツールを押し当てて超音波接合する（請求項６）。
（４）さらに、第４の方法では、超音波ボンディングツールのヘッド面にヒートスプレッダ／金属箔間に指定した接合箇所に対応する凸部を分散形成しておき、ヒートスプレッダに金属箔を超音波接合する際に超音波ボンディングツールのヘッド面に形成した前記凸部を金属箔の上面に押し当て、ツールに押圧力を加えながら超音波接合するものとし（請求項７）、ここで前記凸部は角柱，円柱もしくはテーパー付き角柱，円柱のいずれかになり、その突き出し高さをボンディングツールのヘッド面に併設して形成した前記ローレットの突起（第１の方法）よりも高く設定する（請求項８）。 In order to achieve the above object, a semiconductor device according to the present invention has a power semiconductor chip mounted on a conductor pattern of an insulating substrate, a conductive heat spreader mounted on the upper surface of the semiconductor chip, and a main electrode surface of the semiconductor chip. And solder bonding between them, and a superposition of a strap-like metal foil as a wiring lead member on the upper surface of the heat spreader and ultrasonic bonding. It is assumed that ultrasonic bonding is performed by dispersing in the overlapping surface area of the heat spreader.
According to the present invention, the following manufacturing method is applied to the manufacturing process of the semiconductor device, and the metal foil is ultrasonically bonded to the upper surface of the heat spreader. That is,
(1) In the first method, a protruding knurl is formed on the head surface of an ultrasonic bonding tool applied to the ultrasonic bonding step, and the metal foil of the wiring lead is bonded to the upper surface of the heat spreader. Ultrasonic bonding is performed by pressing the protrusion on the knurled surface formed on the bonding tool against the upper surface of the metal foil.
(2) In the second method, with respect to the metal foil to be ultrasonically bonded to the upper surface of the heat spreader, the bonding protrusions that protrude toward the heat spreader are dispersed and press-formed at a predetermined joint position, and the metal foil is pressed. When bonding to the heat spreader, the protrusion is superimposed on the upper surface of the heat spreader, and then ultrasonic bonding is performed by pressing an ultrasonic bonding tool on the upper surface of the metal foil (Claim 3), where the bonding protrusion is , Dimple shape (Claim 4), or linear protrusion (Claim 5) extending in parallel with the amplitude direction of ultrasonic vibration applied to the bonding tool.
(3) Further, in the third manufacturing method, instead of forming the joining protrusions on the metal foil, the joining protrusions are dispersedly formed on the upper surface of the heat spreader and formed on the heat spreader when the metal foil is ultrasonically joined to the heat spreader. A flat metal foil is overlaid on the bonding protrusions, and an ultrasonic bonding tool is pressed against the upper surface of the metal foil to ultrasonically bond (Claim 6).
(4) Furthermore, in the fourth method, convex portions corresponding to the joint portions designated between the heat spreader / metal foil are dispersedly formed on the head surface of the ultrasonic bonding tool, and the metal foil is ultrasonically bonded to the heat spreader. The convex portion formed on the head surface of the ultrasonic bonding tool is pressed against the upper surface of the metal foil, and ultrasonic bonding is performed while applying a pressing force to the tool (Claim 7), where the convex portion is a prism. , A cylinder, a tapered prism, or a cylinder, and the protruding height is set higher than the protrusion of the knurling (first method) formed adjacent to the head surface of the bonding tool (Claim 8). .

上記のように、半導体チップに半田接合したヒートスプレッダの上面に配線リードとしての金属箔を重ねて超音波接合する際に、半導体チップの通電容量に見合ったヒートスプレッダ／金属箔間の通電路を形成する接合箇所をヒートスプレッダと金属箔との重なり面域に分散させ、ヒートスプレッダに金属箔を超音波接合する際には、超音波ボンディングツールより印加する押圧荷重，超音波振動を、金属箔の下面あるいはヒートスプレッダの上面に形成した接合突起，もしくはボンディングツールのヘッド面に形成したローレットの突起，凸部を介して前記の接合箇所へ集中的に加えて超音波接合することにより、ヒートスプレッダ／金属箔間に所要の接合面積に見合った通電路を確保することができる。
しかも、超音波ボンディングツールに加える押圧荷重，超音波振動エネルギーは、ヒートスプレッダ／金属箔間の重なり面域に分散して指定した接合箇所を接合するのに必要な値に設定すれば十分で、過大な押圧荷重，超音波振動エネルギーを加える必要がない。 As described above, when the metal foil as the wiring lead is superposed on the upper surface of the heat spreader solder-bonded to the semiconductor chip and ultrasonically bonded, a current path between the heat spreader / metal foil corresponding to the current-carrying capacity of the semiconductor chip is formed. When the joints are dispersed in the overlapping area of the heat spreader and the metal foil, and the metal foil is ultrasonically bonded to the heat spreader, the pressure load and ultrasonic vibration applied by the ultrasonic bonding tool are applied to the lower surface of the metal foil or the heat spreader. It is necessary between the heat spreader / metal foil by performing ultrasonic bonding by intensively applying the bonding protrusions formed on the upper surface of the metal or the knurled protrusions or protrusions formed on the head surface of the bonding tool to the above-mentioned bonding points. An energization path commensurate with the bonding area can be secured.
Moreover, it is sufficient to set the pressure load and ultrasonic vibration energy applied to the ultrasonic bonding tool to the values required to bond the specified joints in the overlapping area between the heat spreader and the metal foil. It is not necessary to apply a large pressing load and ultrasonic vibration energy.

これにより、超音波接合の過程で半導体チップ，および半導体チップ／ヒートスプレッダ間の半田接合層に伝播する超音波振動を小さく抑えてクラック発生のダメージを防ぎつつ、ヒートスプレッダ／金属箔間には通電に必要な接合面積を確保して超音波接合することができる。加えて、ヒートスプレッダを付設したことで半導体チップの放熱性向上と均温化が図れ、また配線リードにストラップ状の金属箔を採用したことで、従来のワイヤ配線構造と比べてボンディング工数，リードタイムを大幅に縮減して、低コストかつ信頼性の高い半導体装置を提供できる。
また、半導体装置の製造方法に関して、超音波ボンディングツールのヘッド面に形成した凸部を金属箔の上面に押し当てて超音波接合を行うようにした本発明の第４の方法によれば、金属箔あるいはヒートスプレッダに接合突起を形成した方法と同等な効果が得られ、しかも金属箔，ヒートスプレッダの部品に接合突起をあらかじめ形成しておく加工工程が省けて製造コストの低減化が図れる。 As a result, it is necessary to energize between the heat spreader and the metal foil while minimizing the ultrasonic vibration propagating to the semiconductor chip and the solder bonding layer between the semiconductor chip and the heat spreader during the ultrasonic bonding process to prevent damage from cracks. It is possible to ensure ultrasonic bonding with a sufficient bonding area. In addition, the heat spreader is attached to improve the heat dissipation and temperature uniformity of the semiconductor chip, and the strap-like metal foil is used for the wiring lead, so that the bonding man-hours and lead time are compared with the conventional wire wiring structure. Can be greatly reduced, and a low-cost and highly reliable semiconductor device can be provided.
In addition, according to the fourth method of the present invention in which the convex portion formed on the head surface of the ultrasonic bonding tool is pressed against the upper surface of the metal foil for ultrasonic bonding, The same effect as the method of forming the bonding protrusions on the foil or the heat spreader can be obtained, and the manufacturing process for forming the bonding protrusions on the metal foil and heat spreader parts in advance can be omitted, thereby reducing the manufacturing cost.

以下、本発明の実施の形態を図１〜図７に示す実施例に基づいて説明する。なお、実施例の図中で図８に対応する部材には同じ符号を付してその説明は省略する。
すなわち、本発明による半導体装置は、図１Ａで示すように金属ベース１に搭載した絶縁基板２に半田マウントしたＩＧＢＴ４に対し、該ＩＧＢＴ４の上面にヒートスプレッダ７を配置してＩＧＢＴの主電極面に半田接合した上で、このヒートスプレッダの上面に配線リードとしてストラップ状の金属箔１１を重ねせて超音波接合するようにした配線構造を備えた構成とし、その半導体装置の製造工程に以下述べる実施例の方法を適用してヒートスプレッダ／金属箔間に所要接合面積の通電路を確保して超音波接合を行うようにしたもので、次にその実施例を請求項別に説明する。 Hereinafter, embodiments of the present invention will be described based on examples shown in FIGS. In addition, in the figure of an Example, the same code | symbol is attached | subjected to the member corresponding to FIG. 8, and the description is abbreviate | omitted.
That is, in the semiconductor device according to the present invention, as shown in FIG. 1A, with respect to the IGBT 4 solder-mounted on the insulating substrate 2 mounted on the metal base 1, the heat spreader 7 is disposed on the upper surface of the IGBT 4 and soldered to the main electrode surface of the IGBT. After the bonding, a structure having a wiring structure in which a strap-like metal foil 11 is superposed on the upper surface of the heat spreader as a wiring lead and ultrasonically bonded is provided. The method is applied to secure a current-carrying path of a required bonding area between the heat spreader / metal foil and perform ultrasonic bonding. The embodiment will be described in the following claims.

まず、本発明による半導体装置の組立構造および請求項２に対応する製造方法の実施例を図１Ａ〜図１Ｄにより説明する。なお、図１Ａは半導体モジュールの組立構造図、図１Ｂはヒートスプレッダ／金属箔間の超音波接合時の状態を表す図、図１Ｃは超音波接合後の状態を表す平面図、図１Ｄは超音波接合後における半導体チップ／ヒートスプレッダ間の半田接合部の状態を表す平面図である。
この実施例では図５に示した従来構造のアルミワイヤ９（配線リード）に替えてストラップ状の金属箔１１を採用し、この金属箔１１をボンディングツールとしての超音波ホーン１２によりヒートスプレッダ７の上面に超音波接合した配線構造になる。
ここで、金属箔１１は銅箔あるいはアルミ箔を採用したもので、その断面積は半導体チップであるＩＧＢＴ４の電流容量に対応して次のように選定する。すなわち、図８の配線構造において線径φ３００μｍのアルミワイヤを６本用いていたとすれば、アルミワイヤの総本数（６本分）の断面積は0.４２ｍｍ２である。したがって、金属箔１１の所要断面積をアルミワイヤ９の総本数の断面積よりも大きく選定するものとし、例えば金属箔１１のストラップ幅を２ｍｍとしてアルミ箔の場合には厚さを0.２１２ｍｍ以上にすればよい。また、アルミに比べて導電率が高い銅箔を採用した場合には、アルミ箔と配線抵抗を同じとして銅箔の必要な厚さを０．０６３５ｍｍに薄くすることが可能であるが、ハンドリング性を考慮して厚さは0.１ｍｍ以上とするのがよい。 First, an assembly structure of a semiconductor device according to the present invention and an embodiment of a manufacturing method corresponding to claim 2 will be described with reference to FIGS. 1A to 1D. 1A is an assembly structure diagram of a semiconductor module, FIG. 1B is a diagram showing a state at the time of ultrasonic bonding between a heat spreader / metal foil, FIG. 1C is a plan view showing a state after ultrasonic bonding, and FIG. 1D is an ultrasonic wave It is a top view showing the state of the solder joint part between the semiconductor chip / heat spreader after joining.
In this embodiment, a strap-like metal foil 11 is employed instead of the aluminum wire 9 (wiring lead) having the conventional structure shown in FIG. 5, and this metal foil 11 is used as an upper surface of the heat spreader 7 by an ultrasonic horn 12 as a bonding tool. The wiring structure is ultrasonically bonded.
Here, the metal foil 11 employs a copper foil or an aluminum foil, and its cross-sectional area is selected as follows according to the current capacity of the IGBT 4 which is a semiconductor chip. That is, if six aluminum wires having a wire diameter of 300 μm are used in the wiring structure of FIG. 8, the cross-sectional area of the total number of aluminum wires (for six wires) is 0.42 mm 2 . Therefore, the required cross-sectional area of the metal foil 11 is selected to be larger than the cross-sectional area of the total number of the aluminum wires 9, and for example, when the strap width of the metal foil 11 is 2 mm and the aluminum foil is used, the thickness is 0.212 mm or more. You can do it. In addition, when a copper foil having a higher conductivity than aluminum is used, the required thickness of the copper foil can be reduced to 0.0635 mm with the same wiring resistance as the aluminum foil. In consideration of the above, the thickness should be 0.1 mm or more.

一方、超音波ホーン１２については、接合部材（金属箔１１）に押し当てるヘッド面にローレット加工を施して例えは０.１〜１.０ｍｍピッチに並ぶ三角錐の突起１２ａを形成しておき、このローレット加工面を金属箔１１の上面に押し当てて押圧荷重Ａおよび超音波振動Ｂを当接箇所に分散して集中的に加えるようにしている。
上記の条件でヒートスプレッダ／金属箔間の超音波接合を行うと、超音波ホーン１２から接合面に加わる押圧荷重Ａ，超音波振動Ｂが前記ローレットの突起１２ａと当接した箇所に集中してこの部分が他の面域に先行して超音波接合されるようになる。なお、超音波ホーン１２に加える押圧荷重Ａ，および超音波振動Ｂのパワーについてはあらかじめ適正値に設定しておき、所定の接合時間が経過して前記接合箇所における接合面積の合計が所要の通電量に見合った面積に達したところで、接合面積がそれ以上に拡大する以前に超音波振動を停止して接合を終了する。 On the other hand, for the ultrasonic horn 12, the head surface pressed against the joining member (metal foil 11) is knurled to form, for example, triangular pyramidal protrusions 12a arranged at a pitch of 0.1 to 1.0 mm. The knurled surface is pressed against the upper surface of the metal foil 11 so that the pressing load A and the ultrasonic vibration B are dispersed and applied in a concentrated manner at the contact points.
When ultrasonic bonding between the heat spreader / metal foil is performed under the above-described conditions, the pressure load A and ultrasonic vibration B applied to the bonding surface from the ultrasonic horn 12 are concentrated on the portion in contact with the protrusion 12a of the knurl. A part comes to be ultrasonically bonded ahead of other surface areas. Note that the pressure load A and the power of the ultrasonic vibration B applied to the ultrasonic horn 12 are set to appropriate values in advance, and the total joining area at the joining location after the predetermined joining time has elapsed is the required energization. When the area commensurate with the amount is reached, the ultrasonic vibration is stopped and the bonding is terminated before the bonding area further increases.

上記の超音波接合工程においては、ヒートスプレッダ７の上面に平坦なストラップ状の金属箔１１を重ね合わせても、実際には面接触とならずに前記ローレットの突起１２ａに対応する点接触の集合として超音波接合の進行に合わせて点接触部から接合が広がっていく。これにより超音波接合後の状態では図１Ｃで表すように、ヒートスプレッダ／金属箔間の接合界面には金属箔１１とヒートスプレッダ７との間の重なり面域に分散じて超音波接合部１３が超音波振動Ｂの振幅方向に形成され、その接合部１３の合計面積で所要の通電容量に見合った通電路を確保することができる。
一方、上記の方法で超音波接合した半導体モジュールの供試体について発明者等が検証したところ、金属箔／ヒートスプレッダ間の接合箇所，接合面積が供試体によってばらつきの生じることが認められた。また、十分な接合面積を確保するように金属箔に押し当てた超音波ホーンの押圧荷重，超音波パワーを高く設定して超音波接合を行うと、図１Ｄで示すようにヒートスプレッダ７とＩＧＢＴ４の上面電極面との間を接合した半田層８の周縁部（半田フィレット部分）にクラックＣが生じ、またＩＧＢＴ４のチップ自身にもクラック，割れが発生するなどの不具合が認められた。 In the ultrasonic bonding process described above, even if the flat strap-like metal foil 11 is superposed on the upper surface of the heat spreader 7, it does not actually come into surface contact but as a set of point contacts corresponding to the knurled protrusions 12a. As the ultrasonic bonding progresses, the bonding spreads from the point contact portion. Thus, in the state after ultrasonic bonding, as shown in FIG. 1C, the ultrasonic bonding portion 13 is superposed at the bonding interface between the heat spreader / metal foil in the overlapping surface area between the metal foil 11 and the heat spreader 7. An energization path that is formed in the amplitude direction of the sonic vibration B and that corresponds to the required energization capacity can be secured by the total area of the joint portion 13.
On the other hand, when the inventors verified the specimen of the semiconductor module ultrasonically bonded by the above-described method, it was found that the joint location between the metal foil and the heat spreader and the joint area varied depending on the specimen. Further, when ultrasonic bonding is performed by setting the pressure load and ultrasonic power of the ultrasonic horn pressed against the metal foil so as to ensure a sufficient bonding area, ultrasonic bonding is performed as shown in FIG. 1D. Cracks C occurred at the peripheral portion (solder fillet portion) of the solder layer 8 joined with the upper electrode surface, and cracks and cracks were also observed in the IGBT 4 chip itself.

このクラック発生の原因は次のことによると推測される。すなわち、金属箔１１の接合面全域に押し当てた超音波ホーン１２に押圧荷重を掛けた状態で行う超音波接合の進行に伴ってヒートスプレッダ７と金属箔１１との間の接合面積（金属同士の擦動により凝着した面積）が広がっていくと、これにつれ金属箔／ヒートスプレッダ間の摩擦係数が増大して超音波ホーン１２からヒートスプレッダ７を介してその裏面側に接合した半田層８およびＩＧＢＴ８のチップに伝播される超音波振動エネルギーが大きくなる。このために、超音波接合の条件として超音波ホーンに加える押圧荷重，超音波振動エネルギーを大きくすると前記の半田接合層，半導体チップに作用する剪断応力が増大してクラックが発生するものと考えられる。
なお、この場合に超音波ホーン１２に加える押圧荷重Ａ，および超音波振動Ｂのパワーを最適化することでクラック発生を抑えることが可能であるが、実際には接合部材の表面粗さ，うねり，超音波ホーン１２の接触状態などの因子が超音波接合の進行に影響を及ぼすことから、このままでは超音波ホーン１２に加える加圧荷重，超音波パワーの接合条件を一元的に管理して常に適正な超音波接合を行うことが難しい問題が残る。 The cause of this crack generation is presumed to be as follows. That is, with the progress of ultrasonic bonding performed in a state where a pressure load is applied to the ultrasonic horn 12 pressed against the entire bonding surface of the metal foil 11, the bonding area between the heat spreader 7 and the metal foil 11 (the metal-to-metal bonding) As the area of adhesion due to friction increases, the friction coefficient between the metal foil / heat spreader increases and the solder layer 8 and the IGBT 8 bonded to the back side of the ultrasonic horn 12 through the heat spreader 7 are increased. The ultrasonic vibration energy transmitted to the chip is increased. For this reason, if the pressure load applied to the ultrasonic horn and the ultrasonic vibration energy are increased as the ultrasonic bonding conditions, it is considered that the shear stress acting on the solder bonding layer and the semiconductor chip increases and cracks are generated. .
In this case, the generation of cracks can be suppressed by optimizing the power of the pressing load A and the ultrasonic vibration B applied to the ultrasonic horn 12, but in reality the surface roughness and undulation of the joining member Since factors such as the contact state of the ultrasonic horn 12 affect the progress of ultrasonic bonding, the bonding conditions of the pressure load and ultrasonic power applied to the ultrasonic horn 12 are managed in an integrated manner. It remains difficult to perform proper ultrasonic bonding.

次に、先記実施例１で述べた方法を改良し、半導体チップ，半導体チップ／ヒートスプレッダ間の半田接合層のクラック発生によるダメージを排除して適正な超音波接合が再現性よく行えるようにした本発明の請求項３〜５に対応する製造方法の実施例を図２〜図４で説明する。すなわち、先記の実施例１では配線リードとして平坦なストラップ状の金属箔１１を採用し、これにボンディングツールとして先端面にローレット加工を施して突起１２ａを形成した超音波ホーン１２（図１Ｂ参照）を用いて接合箇所を分散させるようにしているが、前述のように金属箔１１が平坦なストラップであるとその表面粗さ，うねり，および超音波ホーン１２との当接状態の影響を受けて図１Ｃに示した接合部１３の接合面積がばらつくようになると言った問題点が残る。
そこで、上記問題を解消するために、この実施例では金属箔１１に対し、ヒートスプレッダ７との重なり面域に指定した接合箇所に次記の接合突起を分散するようにしている。すなわち、図２（ａ），（ｂ）では金属箔１１に接合突起として円形状のディンプル１１ａをあらかじめプレス形成しておき、この金属箔１１をヒートスプレッダ上面に超音波接合する際には、図３（ａ）で示すように金属箔１１に形成したディンプル１１ａの凸面をヒートスプレッダ７の上面に向けて重ね合わせた上で、金属箔１１の上面側に超音波ホーン１２を押し当てて超音波接合を行うようにしている。なお、超音波ホーン１２の端面には図１Ｂに示したと同様なローレット加工を施して突起１２ａを形成しておき、超音波接合の際に加えた矢印Ｂ方向の超音波振動でホーン／金属箔間がスリップするのを防ぎ、超音波振動エネルギーが前記の接合突起１１ａを介してヒートスプレッダ７との接合界面に効率よく伝播するようにするのがよい。これにより、超音波接合後の状態では図３（ｂ）で表すように、ヒートスプレッダ／金属箔の接合界面には前記ディンプル１１ａに対応した楕円形状の接合部１３が分散して形成されることになる。 Next, the method described in Example 1 was improved so that damage caused by cracks in the solder joint layer between the semiconductor chip and the semiconductor chip / heat spreader was eliminated, and proper ultrasonic bonding could be performed with good reproducibility. An embodiment of a manufacturing method corresponding to claims 3 to 5 of the present invention will be described with reference to FIGS. That is, in the first embodiment, a flat strap-shaped metal foil 11 is used as a wiring lead, and an ultrasonic horn 12 having a protrusion 12a formed by knurling the tip surface as a bonding tool (see FIG. 1B). ) Is used to disperse the joints. However, if the metal foil 11 is a flat strap as described above, it is affected by the surface roughness, undulation, and the contact state with the ultrasonic horn 12. Thus, there remains a problem that the bonding area of the bonding portion 13 shown in FIG. 1C varies.
Therefore, in order to solve the above-described problem, in this embodiment, the following bonding protrusions are dispersed at the bonding points designated in the overlapping surface area with the heat spreader 7 with respect to the metal foil 11. That is, in FIGS. 2 (a) and 2 (b), when circular dimples 11a are formed in advance on the metal foil 11 as bonding protrusions, and this metal foil 11 is ultrasonically bonded to the upper surface of the heat spreader, FIG. As shown in (a), the convex surface of the dimple 11a formed on the metal foil 11 is superimposed on the upper surface of the heat spreader 7, and then the ultrasonic horn 12 is pressed against the upper surface side of the metal foil 11 to perform ultrasonic bonding. Like to do. The end face of the ultrasonic horn 12 is knurled in the same manner as shown in FIG. 1B to form a protrusion 12a, and the horn / metal foil is subjected to ultrasonic vibration in the direction of arrow B applied during ultrasonic bonding. It is preferable to prevent the gap from slipping and to efficiently propagate the ultrasonic vibration energy to the bonding interface with the heat spreader 7 through the bonding protrusion 11a. As a result, in the state after ultrasonic bonding, as shown in FIG. 3B, the elliptical bonding portions 13 corresponding to the dimples 11a are formed in a dispersed manner at the heat spreader / metal foil bonding interface. Become.

ここで、前記ディンプル１１ａの径サイズ，および個数は次のように設定する。すなわち、図８に示した従来の配線構造で線径φ３００μｍのアルミワイヤ９を６本使用していたとすれば、これに合わせてアルミワイヤ６の接合部と同等な面積のディンプル１１ａを箔面上の６箇所に分散して形成するものとする。
これにより、超音波接合時には、超音波ホーン１２から加える押圧荷重Ａ，超音波振動Ｂが前記ディンプル１１ａとヒートスプレッダ７との当接面に集中してこの部分が超音波接合されるようになる。したがって、超音波ホーン１２から接合部材の全面域に押圧荷重Ａを加えて超音波接合を行う方法と比べ、低荷重でも指定した箇所（ディンプル１１ａ）を確実に接合できる。しかも、この実施例では必要な数のディンプル１１ａを金属箔１１とヒートスプレッダ７との重なり面域に分散形成したことで、配線リードとしてＩＧＢＴ４から取り出す電流の局部集中を避けつつ所要の通電容量に見合った接合面積の通電路を確保でき、先記の実施例１で問題となっていた接合箇所，接続面積のバラツキ問題を効果的に解消できる。 Here, the diameter size and the number of the dimples 11a are set as follows. That is, if six aluminum wires 9 having a diameter of 300 μm are used in the conventional wiring structure shown in FIG. 8, dimples 11a having an area equivalent to the joint portion of the aluminum wires 6 are formed on the foil surface accordingly. It is assumed that it is formed in a dispersed manner at these six locations.
Thereby, at the time of ultrasonic bonding, the pressing load A and the ultrasonic vibration B applied from the ultrasonic horn 12 are concentrated on the contact surface between the dimple 11a and the heat spreader 7, and this portion is ultrasonically bonded. Therefore, compared with the method in which the ultrasonic load is applied to the entire area of the bonding member from the ultrasonic horn 12 and the ultrasonic bonding is performed, the designated portion (dimple 11a) can be reliably bonded even at a low load. In addition, in this embodiment, a necessary number of dimples 11a are dispersedly formed in the overlapping surface area of the metal foil 11 and the heat spreader 7, thereby avoiding local concentration of the current taken out from the IGBT 4 as a wiring lead to meet the required current carrying capacity. In addition, it is possible to secure a current-carrying path with a large bonding area, and to effectively eliminate the problem of variation in the bonding location and the connection area, which has been a problem in the first embodiment.

また、金属箔１１に形成する接合突起として、図４（ａ），（ｂ）で示すように超音波ホーン１２（図３参照）から加わる超音波振動の振幅方向に沿って延在する直線状の突起１１ｂを金属箔１１の箔面上に分散してプレス形成して実施することもできる。なお、この直線状突起１１ｂのサイズ，数は図２に示したディンプル状接合突起１１ａと同様に所要の通電容量に合わせて設定するものとする。これにより図２，図３で述べたと同等な効果が得られる。
なお、金属箔１１の面上に形成した接合突起は、図２の円形状ディンプル１１ａ，図４の直線状の突起１１ｂに限定されるものではなく、超音波ホーン１２からの超音波振動を集中荷重できれば任意の形状でもよい。 Moreover, as a joining protrusion formed in the metal foil 11, as shown in FIGS. 4A and 4B, a linear shape extending along the amplitude direction of ultrasonic vibration applied from the ultrasonic horn 12 (see FIG. 3). The protrusions 11b can be dispersed on the foil surface of the metal foil 11 and press formed. Note that the size and number of the linear protrusions 11b are set in accordance with the required energization capacity in the same manner as the dimple-shaped bonding protrusions 11a shown in FIG. Thereby, the same effect as described in FIGS. 2 and 3 can be obtained.
The joining protrusions formed on the surface of the metal foil 11 are not limited to the circular dimples 11a in FIG. 2 and the linear protrusions 11b in FIG. 4, but concentrate ultrasonic vibration from the ultrasonic horn 12. Any shape may be used as long as it can be loaded.

次に、本発明の請求項６に対応する製造方法の実施例を図５（ａ），（ｂ）で説明する。すなわち、先記の実施例２では、金属箔１１に箔面に接合突起として円形状のディンプル１１ａ，あるいは直線状突起１１ｂをプレス形成しておき、ヒートスプレッダ／金属箔間を超音波接合する際に、この接合突起をヒートスプレッダ７の上面に重ねて超音波接合を行うようにしている。
これに対して、この実施例ではヒートスプレッダ７の上面に接合突起７ａとしてダボ状の突起を分散形成しておき、ヒートスプレッダ／金属箔間を超音波接合する際に前記接合突起７ａの上に平坦な金属箔１１を重ね合わせ、その上に超音波ホーン１２を押し当てて超音波接合を行うようにしている。これにより、実施例２と同等な効果を奏することができる。なお、この接合突起７ａはヒートスプレッダ７の製作時に同時成形できる。 Next, an embodiment of the manufacturing method corresponding to claim 6 of the present invention will be described with reference to FIGS. That is, in Example 2 described above, when circular dimples 11a or linear protrusions 11b are press-formed on the metal foil 11 as bonding protrusions on the foil surface, and the heat spreader / metal foil is ultrasonically bonded. The joining protrusions are superposed on the upper surface of the heat spreader 7 for ultrasonic joining.
In contrast, in this embodiment, dowel-shaped protrusions are dispersedly formed on the upper surface of the heat spreader 7 as the bonding protrusions 7a, and when the heat spreader / metal foil is ultrasonically bonded, the flatness is formed on the bonding protrusions 7a. The metal foil 11 is superposed, and an ultrasonic horn 12 is pressed thereon to perform ultrasonic bonding. Thereby, an effect equivalent to that of the second embodiment can be obtained. The joint protrusion 7a can be simultaneously formed when the heat spreader 7 is manufactured.

次に、本発明の請求項７，８に対応する実施例を図６，７で説明する。先記の実施例２，実施例３では接合部材である金属箔１１，あるいはヒートスプレッダ７に接合突起を分散形成した上で、超音波ホーン１２を押し当てて超音波接合を行うようにしているのに対して、この実施例では接合部材に接合突起を形成する代わりに、超音波ボンディングツールである超音波ホーン１２のヘッド面に凸部１２ｂを形成しておく。
この凸部１２ｂは、先記の実施例１（図１Ｂ参照）で超音波ホーン１２のヘッド面にローレット加工した突起１２ａと併設しており、その凸部の突き出し高さはローレットの突起１２ａ（高さ：０．１〜１．０mm）よりも高く設定してローレット加工面から突き出すようにしておく。また、凸部１２ｂの形状は図７（ａ），（ｂ）で示すように角柱，あるいは図７（ｃ），（ｄ）で示すようにテーパ付き円柱などで実施することができる。なお、凸部１２ｂの個数については、図示例のように４箇所に限定されるものではなく、ヒートスプレッダ／金属箔間の通電路として要求される接合面積などの条件により適宜に変更して実施するものとする。 Next, an embodiment corresponding to claims 7 and 8 of the present invention will be described with reference to FIGS. In the above-described second and third embodiments, the joining projections are dispersedly formed on the metal foil 11 or the heat spreader 7 which is a joining member, and then the ultrasonic horn 12 is pressed to perform the ultrasonic joining. On the other hand, in this embodiment, instead of forming the bonding protrusion on the bonding member, the convex portion 12b is formed on the head surface of the ultrasonic horn 12 which is an ultrasonic bonding tool.
The protrusion 12b is provided with a protrusion 12a knurled on the head surface of the ultrasonic horn 12 in the first embodiment (see FIG. 1B), and the protrusion height of the protrusion is the knurled protrusion 12a ( The height is set higher than 0.1 to 1.0 mm) so as to protrude from the knurled surface. Moreover, the shape of the convex part 12b can be implemented by a prism as shown in FIGS. 7 (a) and 7 (b) or a tapered cylinder as shown in FIGS. 7 (c) and 7 (d). In addition, about the number of the convex parts 12b, it is not limited to four places like the example of illustration, It implements changing suitably according to conditions, such as a joining area requested | required as a current path between a heat spreader / metal foil. Shall.

そして、超音波ホーン１２を使ってヒートスプレッダ／金属箔間を超音波接合する際には、図６（ａ）のように超音波ホーン１２に押圧荷重Ａを加えてヘッド面に形成した凸部１２ｂを金属箔１１の上面に押し当て、この状態で超音波ホーンより超音波振動Ｂを印加して超音波接合する。これにより、図６（ｂ）のように押圧荷重Ａを受けた超音波ホーンの凸部１２ｂが金属箔１１の箔面に食い込んでその直下の箔部分がヒートスプレッダ７の上面に圧接され、同時にローレット１２ａの突起が金属箔１１の上面に当接して超音波ホーン１２と金属箔１１とがスリップしないようにした状態で、超音波振動Ｂを前記突起１２ｂに対応する箇所の接合界面へ集中的に印加して超音波接合される。
この方法によれば、先記の実施例２，実施例３と同等な接合効果が得られる。しかも、実施例２，３の方法では金属箔１１，ヒートスプレッダ７の各部品ごとに接合突起をプレス成形するために部品のコストが高くなるが、超音波ホーン１２に凸部１２を設けておけば、接合部品の加工が不要となるのでコストの低減化が図れる。 When ultrasonic bonding is performed between the heat spreader and the metal foil using the ultrasonic horn 12, a convex portion 12b formed on the head surface by applying a pressing load A to the ultrasonic horn 12 as shown in FIG. Is pressed against the upper surface of the metal foil 11, and in this state, ultrasonic vibration B is applied from an ultrasonic horn to perform ultrasonic bonding. As a result, the convex portion 12b of the ultrasonic horn that has received the pressing load A as shown in FIG. 6B bites into the foil surface of the metal foil 11, and the immediately lower foil portion is pressed against the upper surface of the heat spreader 7, and at the same time, In a state where the projection of 12a abuts on the upper surface of the metal foil 11 so that the ultrasonic horn 12 and the metal foil 11 do not slip, the ultrasonic vibration B is concentrated on the joint interface corresponding to the projection 12b. Apply and ultrasonic bonding.
According to this method, it is possible to obtain a joining effect equivalent to that of the second and third embodiments. Moreover, in the methods of Examples 2 and 3, the cost of the parts increases because the bonding projections are press-molded for each part of the metal foil 11 and the heat spreader 7, but if the convex portion 12 is provided in the ultrasonic horn 12 In addition, since it is not necessary to process the joined parts, the cost can be reduced.

本発明の実施例１に係わる半導体装置の組立構造図Assembly structure diagram of semiconductor device according to Embodiment 1 of the present invention ヒートスプレッダ／金属箔間の超音波接合時の状態を表す図The figure showing the state at the time of ultrasonic bonding between heat spreader / metal foil 超音波接合後の接合界面状態を表す模式平面図Schematic plan view showing the bonding interface state after ultrasonic bonding 金属箔を超音波接合したヒートスプレッダと半導体チップとの間の半田接合部の状態を表す模式平面図Schematic plan view showing the state of the solder joint between the heat spreader with ultrasonically bonded metal foil and the semiconductor chip 本発明の実施例２に適用するディンプル付き金属箔の形状を表す図で、（ａ），（ｂ）はそれぞれ平面図，および断面図It is a figure showing the shape of the metal foil with a dimple applied to Example 2 of this invention, (a), (b) is a top view and sectional drawing, respectively 実施例２に係わる超音波接合方法の説明図で、（ａ）は２の金属箔をヒートスプレッダに超音波接合する状態を表す図、（ｂ）は接合後の接合界面状態を表す模式平面図It is explanatory drawing of the ultrasonic bonding method concerning Example 2, (a) is a figure showing the state which ultrasonically joins 2 metal foil to a heat spreader, (b) is a schematic plan view showing the joining interface state after joining. 本発明の実施例３に採用する直線状突起付き金属箔の形状を表す図で、（ａ），（ｂ）はそれぞれ平面図，および（ａ）の矢視Ｙ−Ｙ断面図It is a figure showing the shape of the metal foil with a linear protrusion employ | adopted as Example 3 of this invention, (a), (b) is a top view, respectively, and the arrow YY sectional drawing of (a) 本発明の実施例３に係わる超音波接合方法の説明図で、（ａ）は金属箔をヒートスプレッダに超音波接合する状態を表す図、（ｂ）はヒートスプレッダの平面図It is explanatory drawing of the ultrasonic joining method concerning Example 3 of this invention, (a) is a figure showing the state which ultrasonically joins metal foil to a heat spreader, (b) is a top view of a heat spreader. 本発明の実施例４に係わる超音波接合方法の説明図で、（ａ），（ｂ）は超音波接合の進行経過状態を表す図It is explanatory drawing of the ultrasonic joining method concerning Example 4 of this invention, (a), (b) is a figure showing the progress progress state of ultrasonic joining. 図６の超音波接合方法に適用する凸部付き超音波ホーンの構造図で、（ａ），（ｂ）は異なる実施例の側面図，（ｃ），（ｄ）はそれぞれ（ａ），（ｂ）に対応するヘッド面図FIG. 7 is a structural diagram of an ultrasonic horn with a convex portion applied to the ultrasonic bonding method of FIG. 6, (a) and (b) are side views of different embodiments, and (c) and (d) are (a) and (d), respectively. Head view corresponding to b) 半導体チップの上面に半田接合したヒートスプレッダの上面に配線リードとしてボンディングワイヤを超音波接合した従来における半導体モジュールの組立構造図で、（ａ），（ｂ）はそれぞれ平面図，および側面図1A and 1B are an assembly structure diagram of a conventional semiconductor module in which bonding wires are ultrasonically bonded as wiring leads to an upper surface of a heat spreader that is solder-bonded to the upper surface of a semiconductor chip. FIG.

符号の説明Explanation of symbols

１ 金属ベース
２ 絶縁基板
２ｂ 導体パターン
４ ＩＧＢＴ（パワー半導体チップ）
７ ヒートスプレッダ
７ａ 接合突起
８ 半田層
１１ 金属箔
１１ａ ディンプル（接合突起）
１１ｂ 直線状突起（接合突起）
１２ 超音波ホーン
１２ａ ローレット
１２ｂ 凸部
１３ 超音波接合部 DESCRIPTION OF SYMBOLS 1 Metal base 2 Insulating substrate 2b Conductor pattern 4 IGBT (power semiconductor chip)
7 Heat spreader 7a Bonding protrusion 8 Solder layer 11 Metal foil 11a Dimple (bonding protrusion)
11b Linear protrusion (joint protrusion)
12 Ultrasonic horn 12a Knurl 12b Convex part 13 Ultrasonic joint

Claims (8)

絶縁基板にマウントしたパワー半導体チップに対し、該半導体チップの上面に導電性のヒートスプレッダを搭載して半導体チップの主電極面との間を半田接合した上で、ヒートスプレッダの上面に配線リードとしてストラップ状の金属箔を重ねて超音波接合した配線構造になる半導体装置において、金属箔／ヒートスプレッダ間の通電路となる接合箇所を前記金属箔とヒートスプレッダの重なり面域に分散させて超音波接合したことを特徴とする半導体装置。 For a power semiconductor chip mounted on an insulating substrate, a conductive heat spreader is mounted on the upper surface of the semiconductor chip and soldered to the main electrode surface of the semiconductor chip, and then a strap shape is formed as a wiring lead on the upper surface of the heat spreader. In a semiconductor device having a wiring structure in which the metal foils are superposed and ultrasonically bonded, the ultrasonic wave bonding is performed by dispersing the bonding points that become the current paths between the metal foil and the heat spreader in the overlapping surface area of the metal foil and the heat spreader. A featured semiconductor device. 請求項１記載の半導体装置の製造方法であって、その超音波接合工程に適用する超音波ボンディングツールのヘッド面に突起状のローレットを形成しておき、配線リードの金属箔をヒートスプレッダの上面に接合する際に前記ボンディングツールに形成したローレット面の突起を金属箔の上面に押し当てて超音波接合することを特徴とする半導体装置の製造方法。 2. The method of manufacturing a semiconductor device according to claim 1, wherein a protruding knurl is formed on a head surface of an ultrasonic bonding tool applied to the ultrasonic bonding step, and the metal foil of the wiring lead is formed on the upper surface of the heat spreader. A method of manufacturing a semiconductor device, comprising: ultrasonic bonding by pressing a knurled protrusion formed on the bonding tool against an upper surface of a metal foil when bonding. 請求項１記載の半導体装置の製造方法であって、ヒートスプレッダの上面に重ねて超音波接合する金属箔の箔面に、ヒートスプレッダへ向けて凸となる接合突起を分散してプレス成形しておき、金属箔をヒートスプレッダに接合する際に前記突起をヒートスプレッダの上面に重ねた上で、金属箔の上面に超音波ボンディングツールを押し当てて超音波接合することを特徴とする半導体装置の製造方法。 The method for manufacturing a semiconductor device according to claim 1, wherein the bonding protrusions protruding toward the heat spreader are dispersed and press-molded on the foil surface of the metal foil to be ultrasonically bonded to the upper surface of the heat spreader, A method of manufacturing a semiconductor device, wherein when the metal foil is bonded to the heat spreader, the protrusion is superimposed on the upper surface of the heat spreader, and then an ultrasonic bonding tool is pressed against the upper surface of the metal foil to perform ultrasonic bonding. 請求項３記載の製造方法において、金属箔の箔面に分散形成した接合突起がディンプル形状であることを特徴とする半導体装置の製造方法。 4. The method of manufacturing a semiconductor device according to claim 3, wherein the bonding protrusions dispersedly formed on the foil surface of the metal foil have a dimple shape. 請求項３記載の製造方法において、金属箔の箔面に分散形成した接合突起が、ボンディングツールから金属箔の接合面に印加する超音波振動の振幅方向に延在する直線状突起であることを特徴とする半導体装置の製造方法。 4. The manufacturing method according to claim 3, wherein the bonding protrusions dispersedly formed on the foil surface of the metal foil are linear protrusions extending in an amplitude direction of ultrasonic vibration applied from the bonding tool to the bonding surface of the metal foil. A method of manufacturing a semiconductor device. 請求項１記載の半導体装置の製造方法であって、金属箔を重ねて超音波接合するヒートスプレッダの上面に、金属箔に向けて凸となる接合突起を分散形成しておき、金属箔を超音波接合する際に前記接合突起の上に平坦な金属箔を重ねた上で、金属箔の上面に超音波ボンディングツールを押し当てて超音波接合することを特徴とする半導体装置の製造方法。 2. The method of manufacturing a semiconductor device according to claim 1, wherein bonding protrusions projecting toward the metal foil are dispersedly formed on the upper surface of the heat spreader for ultrasonic bonding by overlapping the metal foil, and the metal foil is ultrasonicated. A method of manufacturing a semiconductor device, comprising: superposing a flat metal foil on the joining protrusion when joining and ultrasonically joining the metal foil by pressing an ultrasonic bonding tool on the upper surface of the metal foil. 請求項１記載の半導体装置の製造方法であって、その超音波接合工程に適用する超音波ボンディングツールのヘッド面にヒートスプレッダ／金属箔間の接合箇所に対応する凸部を分散形成しておき、ヒートスプレッダに金属箔を超音波接合する際に超音波ボンディングツールのヘッド面に形成した前記凸部を金属箔の上面に押し当て、ツールに押圧力を加えながら超音波接合することを特徴とする半導体装置の製造方法。 The method for manufacturing a semiconductor device according to claim 1, wherein a convex portion corresponding to a joint portion between the heat spreader / metal foil is dispersedly formed on a head surface of an ultrasonic bonding tool applied to the ultrasonic bonding step. A semiconductor characterized in that when the metal foil is ultrasonically bonded to the heat spreader, the convex portion formed on the head surface of the ultrasonic bonding tool is pressed against the upper surface of the metal foil, and ultrasonic bonding is performed while applying a pressing force to the tool. Device manufacturing method. 請求項７記載の製造方法において、超音波ボンディングツールのヘッド面に形成した凸部が角柱，円柱もしくはテーパー付き角柱，円柱のいずれかになり、その突き出し高さを、前記凸部と併設してボンディングツールのヘッド面に形成したローレットの突起よりも高く設定したことを特徴とする半導体装置の製造方法。 8. The manufacturing method according to claim 7, wherein the convex portion formed on the head surface of the ultrasonic bonding tool is any one of a prism, a cylinder, a tapered prism, and a cylinder, and the protruding height is provided along with the protrusion. A method for manufacturing a semiconductor device, characterized in that it is set higher than a knurled protrusion formed on a head surface of a bonding tool.
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