JP2014187180A - Assembly for semiconductor device, substrate for power module and power module - Google Patents

Assembly for semiconductor device, substrate for power module and power module Download PDF

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JP2014187180A
JP2014187180A JP2013061018A JP2013061018A JP2014187180A JP 2014187180 A JP2014187180 A JP 2014187180A JP 2013061018 A JP2013061018 A JP 2013061018A JP 2013061018 A JP2013061018 A JP 2013061018A JP 2014187180 A JP2014187180 A JP 2014187180A
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semiconductor element
power module
metal layer
layer
aluminum
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JP6011410B2 (en
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Akira Muranaka
亮 村中
Sotaro Oi
宗太郎 大井
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Mitsubishi Materials Corp
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42Wire connectors; Manufacturing methods related thereto
    • H01L2224/47Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481Disposition
    • H01L2224/48135Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip
    • H01L2224/48137Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip the bodies being arranged next to each other, e.g. on a common substrate
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732Location after the connecting process
    • H01L2224/73251Location after the connecting process on different surfaces
    • H01L2224/73265Layer and wire connectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10Details of semiconductor or other solid state devices to be connected
    • H01L2924/11Device type
    • H01L2924/13Discrete devices, e.g. 3 terminal devices
    • H01L2924/1304Transistor
    • H01L2924/1305Bipolar Junction Transistor [BJT]
    • H01L2924/13055Insulated gate bipolar transistor [IGBT]
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181Encapsulation
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/19Details of hybrid assemblies other than the semiconductor or other solid state devices to be connected
    • H01L2924/191Disposition
    • H01L2924/19101Disposition of discrete passive components
    • H01L2924/19107Disposition of discrete passive components off-chip wires

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  • Structures Or Materials For Encapsulating Or Coating Semiconductor Devices Or Solid State Devices (AREA)

Abstract

PROBLEM TO BE SOLVED: To enhance adhesion of the element mounting surface of an insulating substrate for use in a power module to be resin molded and the mold resin, while suppressing occurrence of positional shift or inclination of a semiconductor element.SOLUTION: In an assembly for semiconductor device formed by bonding a metal layer 12 for circuit having the outermost surface composed of copper and a ceramic substrate 11, and further bonding a semiconductor element 3 to the outermost surface with a solder layer 7 interposed therebetween, an aluminum layer 14 is applied to surround a planned bonding area with a width of 1/4 or more of the maximum side length of the semiconductor element 3 in the surface direction, while avoiding the planned bonding area of the semiconductor element 3 and a fillet formation area on the surface of the metal layer 12 for circuit.

Description

本発明は、大電流、高電圧を制御する半導体装置に用いられる半導体装置用接合体、パワーモジュール用基板及びパワーモジュールに関する。   The present invention relates to a joined body for a semiconductor device, a power module substrate, and a power module used in a semiconductor device that controls a large current and a high voltage.

パワーモジュールに用いられる絶縁基板は、一般に絶縁体であるセラミックスや樹脂の両面に金属層がメタライズされる。メタライズされた金属層の一方の面ははんだ等で半導体素子が接合される回路面を構成し、他方の面は、半導体素子の発熱を放熱する放熱面を構成し、この放熱面は、ろう付けやはんだ付け、またはグリスを介して冷却器と接続される。
半導体素子と回路用金属層を接合するはんだの接合信頼性は、回路用金属層の硬さ(変形抵抗)と相関があり、回路用金属層として一般的に用いられる銅とアルミニウムを比較した場合、変形抵抗の大きい銅の方が信頼性は優れる。また、はんだとの濡れ性についても銅の方がアルミニウムよりも優れており、回路用金属層としてアルミニウムを用いる場合は、はんだとの濡れ性向上のために表面にNiめっきが必要となる。回路用金属層として銅を用いた場合、銅とはんだは濡れ性が良好なため、Niめっきは不要となりコスト低減となる。以上のことから、絶縁基板の半導体素子実装面の回路用金属層は銅が望ましい。
Insulating substrates used in power modules are generally metallized on both sides of ceramics or resin, which are insulators. One side of the metallized metal layer constitutes the circuit surface to which the semiconductor element is joined with solder, etc., and the other side constitutes a heat dissipation surface that dissipates the heat generated by the semiconductor element, and this heat dissipation surface is brazed. Or connected to the cooler via soldering or grease.
Solder joint reliability for joining semiconductor elements and circuit metal layers correlates with the hardness (deformation resistance) of circuit metal layers, when comparing copper and aluminum, which are commonly used as circuit metal layers The reliability of copper having higher deformation resistance is superior. Also, copper is superior to aluminum in terms of wettability with solder. When aluminum is used as a circuit metal layer, Ni plating is required on the surface to improve wettability with solder. When copper is used as the circuit metal layer, since copper and solder have good wettability, Ni plating is not necessary and the cost is reduced. From the above, copper is desirable for the circuit metal layer on the semiconductor element mounting surface of the insulating substrate.

一方で、半導体素子をはんだ付けした後にこれらを熱硬化性樹脂により封止する構造の場合、半導体素子とリードフレームを電気的に接続するワイヤボンドを行った後に、樹脂封止されるが、銅はアルミニウムよりも樹脂との密着強度が劣り、封止樹脂と銅間に剥離が生じることがあった。特に、湿度の高い環境等で使用した場合、剥離による耐湿性の低下によって、電流リークやワイヤの腐食による信頼性低下や、樹脂により変形を抑制されていたワイヤボンディングと半導体素子の接続部が変形しやすくなり断線に至る等の課題が生じていた。   On the other hand, in the case of a structure in which semiconductor elements are sealed with a thermosetting resin after soldering the semiconductor elements, the resin elements are sealed after wire bonding for electrically connecting the semiconductor elements and the lead frame is performed. Has a lower adhesion strength to the resin than aluminum, and peeling may occur between the sealing resin and copper. In particular, when used in a high-humidity environment, etc., due to a decrease in moisture resistance due to peeling, reliability deterioration due to current leakage and wire corrosion, and wire bonding and semiconductor element connections where deformation has been suppressed by the resin are deformed. The problem that it was easy to do and led to disconnection occurred.

リードフレームと封止樹脂との密着性を向上させるため、以下の特許文献が知られている。
特許文献1では、チップマウント部の半導体素子搭載部の周辺に溝を設けておき、その溝を覆うように樹脂封止することにより、チップマウント部と封止樹脂との密着性を向上させている。
特許文献2では、リードフレームの両面にはニッケルめっきを施し、側面に露出する銅を酸化させて酸化膜を形成しておき、その側面も覆うように樹脂封止することにより密着性を向上させている。
In order to improve the adhesion between the lead frame and the sealing resin, the following patent documents are known.
In Patent Document 1, a groove is provided around the semiconductor element mounting portion of the chip mount portion, and resin sealing is performed so as to cover the groove, thereby improving the adhesion between the chip mount portion and the sealing resin. Yes.
In Patent Literature 2, nickel plating is applied to both surfaces of the lead frame, and the copper exposed on the side surface is oxidized to form an oxide film, and the resin sealing is performed to cover the side surface, thereby improving adhesion. ing.

特開平11−163238号公報JP-A-11-163238 特開平6−151486号公報JP-A-6-151486

特許文献1の場合、密着性は溝により形成される凹凸の面積に応じて増加すると考えられるが、その効果は面積に比例するため、例えば密着性を2倍や3倍大きくしようとするには、非常に大きな面積増加が必要となる。
また、特許文献2の場合では、リードフレーム側面の銅を酸化させることで密着強度を向上させているものの、側面以外の密着強度を向上させることはできていない。
さらに、半導体素子をはんだで実装する場合、治具などにより素子の位置ズレを抑制することが必要であるが、リフロー炉などではんだを溶融させた状態で搬送させる際には、はんだの挙動を制御できず、半導体素子の位置ズレや傾きなどを生じるおそれがある。
In the case of Patent Document 1, it is considered that the adhesion increases according to the area of the irregularities formed by the grooves, but since the effect is proportional to the area, for example, to increase the adhesion twice or three times. A very large area increase is required.
In the case of Patent Document 2, although the adhesion strength is improved by oxidizing copper on the side surface of the lead frame, the adhesion strength other than the side surface cannot be improved.
Furthermore, when mounting a semiconductor element with solder, it is necessary to suppress the positional deviation of the element with a jig or the like, but when the solder is transported in a reflow furnace or the like, the behavior of the solder is There is a risk that the semiconductor element cannot be controlled, and the semiconductor element may be misaligned or tilted.

本発明は、このような事情に鑑みてなされたもので、樹脂モールドされるパワーモジュールに使用する絶縁基板の素子実装面とモールド樹脂との密着性を向上させるとともに、半導体素子の位置ズレや傾きなどの発生を抑制することを目的とする。   The present invention has been made in view of such circumstances, and improves the adhesion between an element mounting surface of an insulating substrate used in a resin-molded power module and a molding resin, and also causes a misalignment or inclination of a semiconductor element. The purpose is to suppress the occurrence of such.

本発明の半導体装置用接合体は、最表面が銅により構成された回路用金属層とセラミックス基板とを接合してなり、前記最表面に半導体素子がはんだ層を介して接合される半導体装置用接合体であって、前記回路用金属層の表面における前記半導体素子の接合予定領域及びフィレット形成領域を避けて、前記半導体素子の面方向の最大辺長さの1/4以上の幅で前記接合予定領域を囲むようにアルミニウム層を被覆したことを特徴とする。   The joined body for a semiconductor device of the present invention is for a semiconductor device in which a metal layer for a circuit whose outermost surface is made of copper and a ceramic substrate are joined, and a semiconductor element is joined to the outermost surface via a solder layer. It is a joined body, and avoids a planned joining region and a fillet forming region of the semiconductor element on the surface of the circuit metal layer, and the joining is performed with a width of ¼ or more of the maximum side length in the surface direction of the semiconductor element. An aluminum layer is coated so as to surround the predetermined area.

アルミニウムは銅より樹脂密着性が高いので、銅からなる素子実装面における接合予定領域及びフィレット形成領域を避けてアルミニウム層を被覆したことにより、銅によるはんだ信頼性と、アルミニウム層による樹脂密着性とを両立させることができる。
一方、銅ははんだとの濡れ性が優れるのに対して、アルミニウムははんだとの濡れ性が悪いので、接合予定領域及びフィレット形成領域を囲むようにアルミニウム層が形成されていることにより、アルミニウム層の内周縁を越えるはんだの濡れ広がりを抑制することができる。
Aluminum has higher resin adhesion than copper, so by covering the aluminum layer avoiding the bonding planned area and fillet formation area on the element mounting surface made of copper, the solder reliability by copper and the resin adhesion by aluminum layer Can be made compatible.
On the other hand, copper has excellent wettability with solder, whereas aluminum has poor wettability with solder. Therefore, the aluminum layer is formed so as to surround the region to be joined and the fillet forming region. It is possible to suppress the spread of solder over the inner periphery of the solder.

本発明のパワーモジュール用基板は、前記半導体装置用接合体における前記回路用金属層とは反対面にアルミニウムからなる放熱用金属層が接合されたことを特徴とする。
また、本発明のパワーモジュールは、前記パワーモジュール基板の前記回路用金属層の最表面にはんだ層を介して半導体素子を接合したことを特徴とする。
The power module substrate of the present invention is characterized in that a heat dissipation metal layer made of aluminum is bonded to the surface opposite to the circuit metal layer in the semiconductor device assembly.
The power module of the present invention is characterized in that a semiconductor element is bonded to the outermost surface of the circuit metal layer of the power module substrate via a solder layer.

本発明によれば、樹脂との密着性はアルミニウム層が担い、はんだの接合信頼性は銅からなる金属層の最表面が担うため、接合信頼性を損なうことなく樹脂密着性を向上することができる。また、はんだ溶融時にはんだ外周部がアルミニウム層に濡れないため、溶融時の半導体素子の挙動が一定範囲内に抑制され、はんだ付け時の半導体素子の位置ズレや傾きの発生を抑制することができる。   According to the present invention, the adhesiveness to the resin is borne by the aluminum layer, and the bonding reliability of the solder is borne by the outermost surface of the metal layer made of copper, so that the resin adhesion can be improved without impairing the bonding reliability. it can. In addition, since the outer periphery of the solder does not get wet with the aluminum layer when the solder is melted, the behavior of the semiconductor element at the time of melting is suppressed within a certain range, and the occurrence of misalignment and inclination of the semiconductor element during soldering can be suppressed. .

本発明の一実施形態の半導体装置としてパワーモジュールを示す全体断面図である。It is a whole sectional view showing a power module as a semiconductor device of one embodiment of the present invention. 図1におけるパワーモジュール用基板の縦断面図である。It is a longitudinal cross-sectional view of the board | substrate for power modules in FIG. 図2のパワーモジュール用基板の平面図である。It is a top view of the board | substrate for power modules of FIG. パワーモジュール用基板における半導体素子の接合予定領域付近を示す拡大平面図である。FIG. 3 is an enlarged plan view showing the vicinity of a bonding area of a semiconductor element on a power module substrate. 図4の縦断面図である。It is a longitudinal cross-sectional view of FIG. 図5において半導体素子を実装した状態を示す縦断面図である。It is a longitudinal cross-sectional view which shows the state which mounted the semiconductor element in FIG.

以下、本発明の実施形態について図面を参照して詳細に説明する。
図1は、本発明の半導体装置の一実施形態であるパワーモジュールを示す。このパワーモジュール1は、パワーモジュール用基板2にはんだ付けされた半導体素子3、半導体素子3とリードフレーム4あるいはパワーモジュール用基板2とリードフレーム4とを接続する金属製のボンディングワイヤまたはリボンボンディング等の接続配線5、パワーモジュール用基板2の一部を露出させた状態で全体を封止する封止樹脂6を備えている。符号7は半導体素子3をパワーモジュール用基板2に接合するはんだ層を示す。
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a power module which is an embodiment of the semiconductor device of the present invention. The power module 1 includes a semiconductor element 3 soldered to a power module substrate 2, a metal bonding wire or ribbon bonding for connecting the semiconductor element 3 and the lead frame 4, or the power module substrate 2 and the lead frame 4. The connection wiring 5 and the sealing resin 6 for sealing the whole in a state where a part of the power module substrate 2 is exposed are provided. Reference numeral 7 denotes a solder layer for joining the semiconductor element 3 to the power module substrate 2.

パワーモジュール用基板2は、図2に示すように、絶縁性の高いセラミックス基板11と、このセラミックス基板11の一方の面に配設された回路用金属層12と、セラミックス基板11の他方の面に配設された放熱用金属層13と、回路用金属層12の表面の一部形成されたアルミニウム層14とを備える。
回路用金属層12は、銅又は銅合金(本発明ではこれらを総称して銅と称す)によって構成される。例えば、回路用金属層12として、無酸素銅の圧延板(純度99.99%以上)からなる銅板がセラミックス基板11に接合されることにより形成される。また、回路用金属層12の厚さは、0.2mm〜1.0mmの範囲内で設定することができ、本実施形態では0.3mmの厚さに設定される。
放熱用金属層13は、アルミニウム又はその合金、もしくは銅又はその合金によって構成することができる。例えば、純度が99.9%以上の純アルミニウム圧延材がセラミックス基板11に接合されることにより形成される。また、放熱用金属板の厚さは、0.2mm〜3mmの範囲内で設定することができ、本実施形態では0.5mmの厚さに設定される。
As shown in FIG. 2, the power module substrate 2 includes a highly insulating ceramic substrate 11, a circuit metal layer 12 disposed on one surface of the ceramic substrate 11, and the other surface of the ceramic substrate 11. The heat-dissipating metal layer 13 and the aluminum layer 14 partially formed on the surface of the circuit metal layer 12 are provided.
The circuit metal layer 12 is made of copper or a copper alloy (in the present invention, these are collectively referred to as copper). For example, the circuit metal layer 12 is formed by bonding a copper plate made of oxygen-free copper rolled plate (purity 99.99% or more) to the ceramic substrate 11. The thickness of the circuit metal layer 12 can be set within a range of 0.2 mm to 1.0 mm, and is set to a thickness of 0.3 mm in the present embodiment.
The metal layer 13 for heat dissipation can be comprised with aluminum or its alloy, or copper or its alloy. For example, it is formed by joining a pure aluminum rolled material having a purity of 99.9% or more to the ceramic substrate 11. Moreover, the thickness of the metal plate for heat dissipation can be set in the range of 0.2 mm-3 mm, and is set to the thickness of 0.5 mm in this embodiment.

セラミックス基板11の各面に回路用金属層12、放熱用金属層13を接合する手段は特に限定されるものではないが、本実施形態ではろう付け法によって接合する。
これら金属層12,13をセラミックス基板11にろう付け法により接合する場合、まず回路用金属層12とセラミックス基板11とをAg−Cu−Ti系のろう材を介して積層し、これらを例えば接合温度850℃程度に加熱することで接合する。その後、放熱用金属層13とセラミックス基板11とをAl−Si系のろう材を介して積層し、これらを例えば640℃程度に加熱することで接合すると、パワーモジュール用基板が形成される。
Means for joining the circuit metal layer 12 and the heat radiation metal layer 13 to each surface of the ceramic substrate 11 is not particularly limited, but in this embodiment, the joining is performed by a brazing method.
When these metal layers 12 and 13 are bonded to the ceramic substrate 11 by a brazing method, the circuit metal layer 12 and the ceramic substrate 11 are first laminated via an Ag—Cu—Ti brazing material, and these are bonded, for example, It joins by heating to the temperature of about 850 degreeC. Thereafter, the heat radiation metal layer 13 and the ceramic substrate 11 are laminated via an Al—Si brazing material, and are joined by heating to, for example, about 640 ° C., thereby forming a power module substrate.

回路用金属層12の表面に形成されるアルミニウム層14には、純アルミニウムが好適である。回路用金属層12とアルミニウム層14とを接合する手段は特に限定されるものではないが、ろう付け、スパッタ、蒸着又は固相拡散接合等により実施される。本実施形態では固相拡散接合法を用い、接合温度は530℃とした。   Pure aluminum is suitable for the aluminum layer 14 formed on the surface of the circuit metal layer 12. The means for joining the circuit metal layer 12 and the aluminum layer 14 is not particularly limited, but is performed by brazing, sputtering, vapor deposition, solid phase diffusion bonding, or the like. In this embodiment, the solid phase diffusion bonding method is used, and the bonding temperature is set to 530 ° C.

図3及び図4に示すように、本実施形態におけるアルミニウム層14は、半導体素子3がはんだ付けされる予定の接合予定領域(半導体素子3の平面形状と同じ形状)S及びフィレット形成領域Aを露出させるように開口部15が設けられた構成とされる。なお、その開口部15内には銅の表面が配置されている。
開口部15が接合予定領域Sを露出するように設けられているので、半導体素子3と回路用金属層12とが確実にはんだ付けされる。また、開口部15内に、前記フィレット形成領域Aが設けられているので、はんだ溶融時の表面張力に伴う半導体素子3のセルフアライメント機能を持たせることができる。
フィレット形成領域Aの幅Cは、溶融前のはんだ層7aの厚さをtとした場合、t以上2×t以下が望ましい。この幅Cが溶融前のはんだ層7aの厚さtの1倍未満の場合、はんだ層のフィレット部Fが形成されず、接合信頼性が低下する。また、前記幅Cが溶融前のはんだ層7aの厚さtの2倍を超える場合、前述したセルフアライメント性及び封止樹脂の密着性が損なわれる。
本実施形態では、図4に示すように、前記幅Cは溶融前のはんだ層7aの厚さtと同じ200μmとした。なお、前記フィレット形成領域Aは接合予定領域Sを取り囲む形状とされている。
また、アルミニウム層14の厚さは50μm以上1mm以下の範囲内で設定することができ、本実施形態では、150μmに設定される。
As shown in FIG. 3 and FIG. 4, the aluminum layer 14 in the present embodiment includes an area to be joined (same shape as the planar shape of the semiconductor element 3) S and a fillet forming area A to which the semiconductor element 3 is to be soldered. It is set as the structure by which the opening part 15 was provided so that it might expose. A copper surface is disposed in the opening 15.
Since the opening 15 is provided so as to expose the bonding planned region S, the semiconductor element 3 and the circuit metal layer 12 are securely soldered. Further, since the fillet forming region A is provided in the opening 15, it is possible to provide a self-alignment function of the semiconductor element 3 accompanying the surface tension at the time of solder melting.
The width C of the fillet forming region A is preferably t or more and 2 × t or less, where t is the thickness of the solder layer 7a before melting. When the width C is less than 1 times the thickness t of the solder layer 7a before melting, the fillet portion F of the solder layer is not formed, and the bonding reliability is lowered. Further, when the width C exceeds twice the thickness t of the solder layer 7a before melting, the self-alignment property and the adhesiveness of the sealing resin described above are impaired.
In this embodiment, as shown in FIG. 4, the width C is set to 200 μm, which is the same as the thickness t of the solder layer 7a before melting. The fillet forming area A has a shape surrounding the bonding scheduled area S.
The thickness of the aluminum layer 14 can be set within a range of 50 μm or more and 1 mm or less, and is set to 150 μm in this embodiment.

また、図4に示すように、本実施形態ではアルミニウム層14の幅(アルミニウム層14の開口部15の内周縁からの幅)Wは、半導体素子3の平面形状(接合予定領域S)における長辺の長さ(図4では半導体素子3の平面形状が正方形としているが、長方形の場合には長い方の寸法)をLとしたときに、L×1/4以上とされている。
アルミニウム層14の幅WがL×1/4未満であると、クラックの進展が半導体素子3まで至るおそれがあり、半導体素子3と接続配線5との接続の信頼性を低下させる。
また、封止樹脂6との密着性をより向上させるためには、アルミニウム層14はフィレット形成領域A及び半導体素子3の接合予定領域Sを除いた回路用金属層12の全体を覆うことがより望ましい。
As shown in FIG. 4, in this embodiment, the width of the aluminum layer 14 (the width from the inner peripheral edge of the opening 15 of the aluminum layer 14) W is the length in the planar shape (scheduled junction region S) of the semiconductor element 3. When the length of the side (in FIG. 4, the planar shape of the semiconductor element 3 is a square but the longer dimension in the case of a rectangle) is L, it is L × 1/4 or more.
If the width W of the aluminum layer 14 is less than L × 1/4, the crack may possibly reach the semiconductor element 3, and the connection reliability between the semiconductor element 3 and the connection wiring 5 is lowered.
In order to further improve the adhesion with the sealing resin 6, the aluminum layer 14 covers the entire circuit metal layer 12 except for the fillet formation region A and the region to be bonded S of the semiconductor element 3. desirable.

このように構成されるパワーモジュール用基板2のアルミニウム層14により囲まれた回路用金属層12の銅表面に半導体素子3をはんだ付けにより接合する。はんだ材は、Sn−Ag−Cu系はんだ(例えば、Sn−3%Ag−0.5%Cu)やSn−Sb系はんだ(例えば、Sn−3.9%Ag−0.6%Cu−3.0%Sb)などの鉛フリーはんだとし、溶融前のはんだ層7aの厚さを50〜400μmの範囲内とする。本実施形態では200μmに設定した。また、半導体素子3としてはIGBT素子(平面寸法が例えば10mm×10mm)が使用される。   The semiconductor element 3 is joined to the copper surface of the circuit metal layer 12 surrounded by the aluminum layer 14 of the power module substrate 2 thus configured by soldering. The solder material is Sn-Ag-Cu solder (for example, Sn-3% Ag-0.5% Cu) or Sn-Sb solder (for example, Sn-3.9% Ag-0.6% Cu-3). 0.0% Sb), etc., and the thickness of the solder layer 7a before melting is in the range of 50 to 400 μm. In this embodiment, it is set to 200 μm. Further, as the semiconductor element 3, an IGBT element (planar dimension is, for example, 10 mm × 10 mm) is used.

この半導体素子3を実装した後、半導体素子3とリードフレーム4、アルミニウム層14とリードフレーム4をそれぞれ接続配線5により電気的に接続する。接続配線5に用いられるワイヤやリボンは一般的にアルミニウムや銅材が使用される。例えば、線径500μmのアルミニウム製ワイヤによりボンディングされる。リードフレーム4は電気伝導性に優れるアルミニウムや銅材により形成される。このリードフレーム4の板厚は1〜5mmに設定され、本実施形態では厚さ2mmのアルミニウム材が用いられる。 After mounting the semiconductor element 3, the semiconductor element 3 and the lead frame 4, and the aluminum layer 14 and the lead frame 4 are electrically connected by the connection wiring 5. The wire and ribbon used for the connection wiring 5 are generally made of aluminum or copper. For example, bonding is performed with an aluminum wire having a wire diameter of 500 μm. The lead frame 4 is formed of aluminum or copper material having excellent electrical conductivity. The lead frame 4 has a plate thickness of 1 to 5 mm. In this embodiment, an aluminum material having a thickness of 2 mm is used.

そして、このように構成したパワーモジュール用基板2とリードフレーム4とを封止樹脂用金型に設置し、熱硬化性の封止樹脂(シリカ粒子が分散したエポキシ系樹脂など)を流動させ封止を行う。この場合、パワーモジュール用基板2のほぼ全体が封止樹脂6により封止されるが、放熱用金属層13の表面(セラミックス基板11との接合面とは反対面)が露出するように封止され、その露出面13aにヒートシンク(図示略)が接合される。 Then, the power module substrate 2 and the lead frame 4 configured as described above are installed in a mold for a sealing resin, and a thermosetting sealing resin (such as an epoxy resin in which silica particles are dispersed) is flowed and sealed. Stop. In this case, almost the entire power module substrate 2 is sealed with the sealing resin 6, but sealed so that the surface of the heat dissipation metal layer 13 (the surface opposite to the bonding surface with the ceramic substrate 11) is exposed. Then, a heat sink (not shown) is joined to the exposed surface 13a.

なお、本発明では、セラミックス基板11に回路用金属層12を接合し、その回路用金属層12の一部をアルミニウム層14により被覆した構成体を、接合体と称しており、一実施形態で説明したパワーモジュール以外の他の半導体装置にも適用することができる。   In the present invention, a structure in which a circuit metal layer 12 is bonded to a ceramic substrate 11 and a part of the circuit metal layer 12 is covered with an aluminum layer 14 is referred to as a bonded body. The present invention can also be applied to other semiconductor devices other than the described power module.

パワーモジュール用基板として、回路用金属層を純度99.95%の無酸素銅(20mm×36mmの矩形状で厚さ0.3mm)、セラミックス基板を窒化アルミニウム(AlN)(24mm×40mmの矩形状で厚さ0.635mm)、放熱用金属板に純度99.99%以上(4N−Al)のアルミニウム(22mm×38mmの矩形状で厚さ0.5mm)を用いた。回路用金属層にアルミニウム層を固相拡散接合した後に、IGBT素子(平面サイズ:10mm×10mm)を200μmの厚さのはんだを用いてはんだ付けした。その後、半導体素子とリードフレーム、アルミニウム層とリードフレームをそれぞれ線径500μmのアルミニウム製ワイヤを用いて接続した。その後、熱硬化性樹脂によりモールドして封止した。
回路用金属層に接合したアルミニウム層は接合予定領域及び接合予定領域の外周縁からはんだ層の厚さと同じ200μmの距離の間の領域(フィレット形成領域)を避けるように形成し、その幅Wを表1に示すように変量して、信頼性試験を行った。この信頼性試験は、液槽式の冷熱サイクル試験機とし、−40℃での30分間の保持と125℃での30分間の保持とを3000サイクル繰り返し実施した後に、半導体素子が通電可能であったものを○、通電できなくなったものを×と判定した。
その信頼性試験の結果を表1に示す。
As the power module substrate, the circuit metal layer is 99.95% pure oxygen-free copper (20 mm x 36 mm rectangular shape with a thickness of 0.3 mm), and the ceramic substrate is aluminum nitride (AlN) (24 mm x 40 mm rectangular shape). And a metal plate for heat dissipation, aluminum having a purity of 99.99% or more (4N-Al) (22 mm × 38 mm rectangular shape and 0.5 mm thickness) was used. After solid phase diffusion bonding of the aluminum layer to the circuit metal layer, an IGBT element (planar size: 10 mm × 10 mm) was soldered using a solder having a thickness of 200 μm. Thereafter, the semiconductor element and the lead frame, and the aluminum layer and the lead frame were connected using aluminum wires each having a wire diameter of 500 μm. Thereafter, it was molded and sealed with a thermosetting resin.
The aluminum layer bonded to the circuit metal layer is formed so as to avoid a region (fillet forming region) between the planned bonding region and the outer peripheral edge of the bonding planned region at a distance of 200 μm, which is the same as the thickness of the solder layer. As shown in Table 1, the reliability was tested by changing the variables. This reliability test was conducted using a liquid bath type thermal cycle tester, and after 30 cycles of holding at −40 ° C. for 30 minutes and holding at 125 ° C. for 30 minutes, the semiconductor element could be energized. Were determined to be ○, and those that could not be energized were determined to be ×.
The results of the reliability test are shown in Table 1.

Figure 2014187180
Figure 2014187180

表1の結果からわかるように、アルミニウム層の幅Wを半導体素子の最大辺の長さLの1/4以上とすることにより、接合信頼性の良好なパワーモジュールを得ることができる。   As can be seen from the results in Table 1, a power module with good bonding reliability can be obtained by setting the width W of the aluminum layer to ¼ or more of the length L of the maximum side of the semiconductor element.

なお、本発明は、上記実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。
実施形態では、回路用金属層を銅からなる一層の金属層としたが、最表面を銅とし、セラミックス基板と接合される裏面をアルミニウムとしてもよい。
In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
In the embodiment, the circuit metal layer is a single metal layer made of copper, but the outermost surface may be copper, and the back surface bonded to the ceramic substrate may be aluminum.

1 パワーモジュール(半導体装置)
2 パワーモジュール用基板
3 半導体素子
4 リードフレーム
5 接続配線
6 封止樹脂
7 はんだ層
11 セラミックス基板
12 回路用金属層
13 放熱用金属層
14 アルミニウム層
15 開口部
S 接合予定領域
A フィレット形成領域
1 Power module (semiconductor device)
2 Power Module Substrate 3 Semiconductor Element 4 Lead Frame 5 Connection Wiring 6 Sealing Resin 7 Solder Layer 11 Ceramic Substrate 12 Metal Layer for Circuit 13 Heat Dissipation Metal Layer 14 Aluminum Layer 15 Opening S Joining Area A Fillet Forming Area

Claims (3)

最表面が銅により構成された回路用金属層とセラミックス基板とを接合してなり、前記最表面に半導体素子がはんだ層を介して接合される半導体装置用接合体であって、前記回路用金属層の表面における前記半導体素子の接合予定領域及びフィレット形成領域を避けて、前記半導体素子の面方向の最大辺長さの1/4以上の幅で前記接合予定領域を囲むようにアルミニウム層を被覆したことを特徴とする半導体装置用接合体。   A joined body for a semiconductor device, in which an outermost surface is formed by joining a circuit metal layer made of copper and a ceramic substrate, and a semiconductor element is joined to the outermost surface via a solder layer. The aluminum layer is covered so as to surround the junction region with a width of 1/4 or more of the maximum side length in the surface direction of the semiconductor element, avoiding the junction region and fillet formation region of the semiconductor element on the surface of the layer A bonded assembly for a semiconductor device, characterized by comprising: 請求項1記載の半導体装置用接合体における前記回路用金属層とは反対面にアルミニウムからなる放熱用金属層が接合されたことを特徴とするパワーモジュール用基板。   The power module substrate according to claim 1, wherein a heat dissipation metal layer made of aluminum is bonded to a surface opposite to the circuit metal layer in the bonded body for a semiconductor device. 請求項2記載のパワーモジュール基板の前記回路用金属層の最表面にはんだ層を介して半導体素子を接合したことを特徴とするパワーモジュール。   3. A power module comprising: a semiconductor element bonded to an outermost surface of the circuit metal layer of the power module substrate according to claim 2 via a solder layer.
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