WO2011132670A1 - Wire bonding method for power semiconductor device - Google Patents

Wire bonding method for power semiconductor device Download PDF

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Publication number
WO2011132670A1
WO2011132670A1 PCT/JP2011/059616 JP2011059616W WO2011132670A1 WO 2011132670 A1 WO2011132670 A1 WO 2011132670A1 JP 2011059616 W JP2011059616 W JP 2011059616W WO 2011132670 A1 WO2011132670 A1 WO 2011132670A1
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WIPO (PCT)
Prior art keywords
wire
bonding
joining
ratio
semiconductor element
Prior art date
Application number
PCT/JP2011/059616
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French (fr)
Japanese (ja)
Inventor
友子 山田
正巳 小倉
教人 高柳
潤 加藤
好壱 木村
弥生 松下
文朋 高野
Original Assignee
本田技研工業株式会社
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Publication date
Application filed by 本田技研工業株式会社 filed Critical 本田技研工業株式会社
Priority to JP2012511665A priority Critical patent/JPWO2011132670A1/en
Publication of WO2011132670A1 publication Critical patent/WO2011132670A1/en

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Definitions

  • the present invention relates to a wire bonding method in a power semiconductor device, in which an electrode part of a power semiconductor element and a circuit component to be electrically connected to the electrode part are connected by an aluminum or other metal wire.
  • a power semiconductor device in which a power semiconductor element is sealed in an insulating container is known.
  • the electrode portion of the semiconductor element and the circuit component are connected by a conductive metal wire.
  • a conductive metal wire Generally, an aluminum wire having a diameter of 300 to 500 ⁇ m is selected as the metal wire.
  • the wire tool is pressed against the electrode portion with a predetermined pressing load with a wedge tool while the work including the power semiconductor element is fixed on the support base with a predetermined fixing pressure.
  • An ultrasonic bonding method is adopted in which ultrasonic vibration is applied and one end of the wire is integrally bonded to the electrode portion.
  • a power semiconductor device is required to have a high life resistance and reliability.
  • the durability evaluation ie, power cycle evaluation
  • the durability evaluation is performed by repeatedly conducting energization in accordance with intermittent energization during actual use.
  • power cycle evaluation due to heat generated by repeated energization, thermal strain caused by the difference in thermal expansion coefficient between the semiconductor element and the wire, the wire shape of the wire, and the structure of the semiconductor device acts on the wire junction.
  • a crack may occur in the wire and the bonding electrode in the vicinity of the wire bonding portion, and the crack may propagate toward the central portion of the bonding surface and peel off, which exceeds the allowable current for one wire.
  • the circuit may be broken by the wire being blown or the element being broken.
  • the bonding shape of the wire when defined in a specific range by the bonding length and the bonding width as in Patent Document 2, the bonding shape becomes an oblong shape that is relatively long in the longitudinal direction of the wire. It is difficult to obtain a highly reliable semiconductor device simply by defining the bonding shape of the wires.
  • the conventional method has a narrow tolerance for tilting, and the surface of the element is scratched or mechanically damaged by a wedge tool during the bonding process.
  • the power cycle evaluation (PCT tolerance) of the power semiconductor device is greatly deteriorated.
  • One or more embodiments of the present invention provide a power semiconductor device that has a high power cycle evaluation (PCT withstand capability) and can stably obtain a highly reliable power semiconductor device by making the wire bonding surface shape close to a circle.
  • a wire bonding method is provided.
  • a work WK including a power semiconductor element S is fixed on a support base 3 with a predetermined fixing pressure F, and has an inverted V-shaped cross section.
  • One end portion 1a of the metal wire 1 is pressed against the electrode portion Sa of the power semiconductor element S with a predetermined pressing load P by the wedge tool T having the wire pressing surface Tf.
  • One end portion (1a of the wire 1) is connected to the electrode portion Sa so that the ratio L / W of the joining length L to the joining width W at the joining surface J of the electrode portion Sa is 1 to 1.6. ) Is connected.
  • Sectional drawing of the principal part of the power module which concerns on typical embodiment The top view seen from the direction of the arrow 2 of FIG. 1, and the partial expanded sectional view which expands and shows a wire junction part
  • Process explanatory drawing corresponding to FIG. 1 which demonstrates simply the ultrasonic bonding process for joining a wire edge part to the electrode part of a semiconductor element.
  • Enlarged end view from line 4-4 in Fig. 3 A graph of the relationship between the strain generated under predetermined energization / heating conditions on the bonding surface between the ultrasonically bonded wire and the element electrode and the ratio L / W of the bonding surface, obtained by experiment using the wire diameter as a parameter.
  • a power module PM as a power semiconductor device includes an insulated circuit board C such as a DCB board mounted on a metal base plate B for heat dissipation with solder H1, and the insulated circuit board C. And a plurality of semiconductor elements S mounted on the upper surface of the substrate via solder H2.
  • the semiconductor element S various elements such as IGBT, FWD, or MOS-FET are used.
  • the electrode part Sa exposed on the upper surface of each semiconductor element S and other circuit components (not shown) to be electrically connected to the electrode part (for example, conductor patterns and lead frames exposed on the surface of the insulating circuit board C, the periphery of the semiconductor element S) are connected to each other by a plurality of wires 1 made of aluminum.
  • the wire one end 1a of the work WK is connected to the electrode portion.
  • a method of ultrasonic bonding is adopted in which a predetermined load P and ultrasonic vibration are applied to Sa with a wedge tool T so that one end 1a of the wire is pressure-bonded to the electrode portion Sa and bonded together.
  • the wedge tool T is supported so as to be lifted and lowered above the support base 3 by a lift drive device (not shown).
  • a concave groove 2 having a V-shaped cross section that extends along the longitudinal direction of the wire 1 (left and right in FIG. 3) and can receive the upper half of the wire 1 is formed.
  • a pair of left and right inner surfaces inclined in opposite directions of the concave groove 2 form a downward wire pressing surface Tf having an inverted V-shaped cross section.
  • the bottom surface of the concave groove 2 extends linearly in the middle portion of the groove 2 in the longitudinal direction, but both ends of the longitudinal direction are chamfered 2r in a circular arc shape. During the sonic bonding, the wire 1 is not deeply cut into the upper surface.
  • the work WK in a state where the semiconductor element S is mounted on the metal base plate B via the insulating circuit board C in advance (the state shown in FIG. 3) is placed on the support base 3, and It is fixed with a predetermined fixing pressure F with the clamping device CL.
  • the clamp device CL is disposed on the side of the support base 3 and is capable of engaging and press-contacting the upper both sides of the workpiece WK from above and driving the clamp arm 50 up and down. And a drive mechanism 51 to support the device.
  • ultrasonic bonding is performed on the workpiece WK in a state where the semiconductor element S is mounted on the metal base plate B via the insulating circuit board C (state shown in FIG. 3).
  • a single semiconductor element or a semiconductor element that is simply mounted on an insulated circuit board that is, a metal base plate that is not mounted
  • a workpiece that is, a metal base plate that is not mounted
  • ultrasonic bonding is performed thereon. You may make it implement.
  • the one end portion 1a of the wire 1 whose intermediate portion is guided and supported by the guide means 4 is moved to a position corresponding to the electrode portion Sa of the semiconductor element S, and the wedge tool T is lowered toward the electrode portion Sa.
  • a wire pressing surface Tf having a reverse V-shaped cross section of the tool T one end portion 1a of the wire 1 is pressed from above at a predetermined pressing load P (for example, when the diameter D of the wire 1 is 300 ⁇ m, 400 to 800 gf, or 400 ⁇ m) 800 to 1200 gf, and in the case of 500 ⁇ m, it is pressed at 1000 to 1500 gf).
  • the joining length that is, the length along the longitudinal direction of the wire 1 at the joining surface J
  • the joining width ie, the length across the wire 1.
  • a substantially oval shape having a major axis L and a minor axis W is obtained. Therefore, the closer the W is to L, that is, the closer the ratio L / W is to 1.0, the closer the joint surface J becomes to a circle.
  • the ratio L / W is lower than 1.0, the shape of the bonding surface of the wire becomes longer than necessary in the longitudinal direction of the wire, and the bonding strength of the wire of the electrode portion Sa cannot be obtained sufficiently. As shown in FIG. 4, the laterally spread portion of the joint surface J becomes large, and the tip of the wedge tool T may come into contact with the surface of the semiconductor element S to be damaged or destroyed. Therefore, in the present invention, the lower limit value of the ratio L / W is set to 1.0.
  • the wire 1 has a diameter D of 300 ⁇ m, 400 ⁇ m, and 500 ⁇ m.
  • the joint length L is in the range of 300 to 750 ⁇ m and the joint width W is 300 to 500 ⁇ m.
  • the ratio L / W is set in the range of 1.0 to 1.5.
  • the joint length L is in the range of 400 to 1000 ⁇ m
  • the joint width W is in the range of 400 to 650 ⁇ m
  • the ratio L / W is 1.0. It is set in the range of ⁇ 1.6.
  • the bonding length L is in the range of 500 to 1200 ⁇ m and the bonding width W is in the range of 500 to 750 ⁇ m, and the ratio L / W is 1.0. It is set in the range of ⁇ 1.6.
  • the fixed pressure F applied to the support 3 of the workpiece WK during ultrasonic bonding is slightly different in shape of the joint surface J due to the difference in the fixed pressure, and also has an effect on the durability. For this reason, in a typical embodiment, it is set within the range of 0.2 to 1.0 MPa.
  • the first is a strain generated due to a difference in physical properties between the wire 1 and the bonded surface (element electrode portion Sa), in particular, a difference in thermal expansion coefficient.
  • the second is distortion generated in relation to the wire rigidity according to the shape of the overhead wire and the wire diameter, which is generated by heat generation of the wire 1 itself by energization. As for the former distortion, the absolute amount of distortion generated when the bonding area of the wire 1 is smaller becomes smaller.
  • the strain generated in relation to the latter wire rigidity is generated in the joint surface J in parallel with the overhead wire direction (wire length direction) and promotes the progress of cracks.
  • the strain generated in the length direction can be relaxed and the progress of cracks can be suppressed.
  • a flat ellipse that is longer in the long axis direction (longitudinal direction of the wire) when the bonding surface J is circular so that stress concentration at the front and rear ends of the bonding surface J in the longitudinal direction of the wire is not excessive. It is more advantageous than the shape, and the tolerance is increased.
  • each wire 1 having a diameter D of 300, 400, and 500 ⁇ m is ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method.
  • the relationship between the strain generated on the joint surface J and the ratio L / W of the joint surface J was obtained by experiment, and the result is shown in FIG. According to FIG. 5, it can be seen that the smaller the ratio L / W is, regardless of the wire diameter D, that is, the distortion tends to decrease as the shape of the joint surface J approaches a circle. Then, it is obvious that the generated strain of the joint surface J directly affects the durability (for example, PCT resistance) of the joint surface J, that is, the durability tends to decrease as the generated strain increases. According to the above, regardless of the wire diameter D, it can be seen that as the ratio L / W becomes smaller (that is, the shape of the joint surface J approaches a circle), the durability tends to improve.
  • a predetermined power cycle test is performed on the end portion 1a of each wire 1 having a diameter of 300, 400, and 500 ⁇ m that is ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method, and the resistance (that is, The relationship between the PCT tolerance) and the ratio L / W was examined, and the test results are shown in FIG.
  • a power cycle test for measuring the tolerance for example, a current of about 180 to 250 A is applied to the semiconductor element S through the wire 1 for about 0.3 to 0.6 seconds, and this is applied for an energization interval of about 6 seconds.
  • the life that is, withstand capability.
  • the above energization conditions were determined by specifying a temperature difference before and after energization of the semiconductor element generated by energization.
  • the tolerance of the test accelerated so as to correspond to the estimated energization time (starting frequency) of the automobile is set to 80000 cycles.
  • This 80000 cycle is used as a lower limit target value for ensuring durability. Therefore, the numbers on the vertical axis in FIG. 6 are expressed as an index converted with the lower limit target value (80000 cycles) of the tolerable amount as 1, that is, “withstand amount fluctuation”.
  • the upper limit value of the ratio L / W in the bonding surface shape of the wire 1 having a diameter D of 300 ⁇ m is 1.5, and the ratio in the bonding surface shape of the wire 1 having a diameter D of 400 ⁇ m.
  • the upper limit value of L / W is 1.6, and the upper limit value of the ratio L / W in the bonding surface shape of the wire 1 having a diameter D of 500 ⁇ m is also 1.6.
  • the work WK is fixed at a predetermined fixing pressure F by the clamping device CL, so that the energy at the time of bonding is efficiently transmitted to the wire 1 which is the work, which is necessary for the wire 1 and the element electrode portion Sa. Since there is no need to apply ultrasonic oscillation or pressure, the energy loss during bonding can be reduced and bonding can be performed efficiently, and mechanical damage to the semiconductor element S during bonding can be reduced as much as possible.
  • the semiconductor module PM can be manufactured.
  • the bonding length L of the bonding surface J when applying the ultrasonic vibration is relatively short with respect to the inclination in the longitudinal direction of the wire bonding shape, particularly when the hitting shape of the bonding surface J is elliptical or circular. In the circular shape, the deformation of the joint shape is reduced, the fluctuation of the PCT tolerance is reduced, and a highly reliable joint is obtained.
  • the bonding shape is elliptical when the fixing pressure F is low even with the same bond parameters (excitation frequency, load, time during bonding). Even when the ratio is close to the shape (that is, the ratio L / W becomes larger) and the fixed ratio F is lower, the amount of diffusion of the metal constituting the wire at the time of joining (alloy layer / joining) (Layer thickness) is reduced, the actual bonding area that affects the PCT tolerance is reduced, and the tolerance is reduced.
  • the load P that can set the ratio L / W to 1.0 to 1.6 which is the setting range of the present invention, is 800 gf or more.
  • the setting range of the fixed pressure F that enables the ratio L / W to be set to 1.0 to 1.6 is 0.2 to 0.84 MPa.
  • the upper limit value (0.84 MPa) of the fixed pressure F exceeds a certain value, that is, about 1.0, no actual damage caused by the large fixed pressure F will occur. . Therefore, in the present invention, it is desirable that the fixed pressure F is set to 0.2 to 1.0 MPa for a wire having a diameter D of 400 ⁇ m.
  • the fixed pressure F is preferably set to 0.2 to 1.0 MPa.
  • the ratio L / W between the bonding length L and the bonding width W of the bonding surface J of the wire 1 having a diameter of 300 to 500 ⁇ m to the electrode portion Sa of the semiconductor element S. Is limited to a specific range (ie, 1.0 to 1.5 for a 300 ⁇ m wire and 1.0 to 1.6 for 400 and 500 ⁇ m wires), the shape of the joint surface J is as circular as possible. Can be approached.
  • the joint surface J By making the shape of the joint surface J as close to a circle as possible, it becomes a wire joint surface shape that can suppress the development of strain and cracks generated at the joint part of ultrasonic bonding as small as possible, and the joint surface shape is thus circular.
  • the allowable width with respect to the inclination of the object to be joined (electrode part Sa of the semiconductor element S) can be increased as much as possible.
  • the mechanical damage that the semiconductor element S receives from the wedge tool T during ultrasonic bonding can be reduced. As a result, it is possible to stably manufacture a power semiconductor module PM having a high withstand capability and high reliability.
  • the wire is made of aluminum, but in the present invention, the wire may be made of a conductive metal or alloy other than aluminum.

Abstract

Disclosed is a wire bonding method for a power semiconductor device, wherein when bonding one end (1a) of a wire (1) to an electrode part (Sa), a workpiece (WK) comprising a power semiconductor element (S) is fixed on a support (3) by a specified fixing pressure (F), and ultrasonic vibration is applied while the end (1a) of the wire (1) is pressed against the electrode part (Sa) with a specified pressing force (P) by a wedge tool (T) with an inverted V-shape wire pressing surface (Tf) in cross-section. A bond length (L) and a bond width (W) of a bond surface (J) of the wire end (1a) and the electrode part (Sa) are set such that the ratio (L/W) is within the range 1.0-1.6.

Description

パワー半導体装置におけるワイヤボンディング方法Wire bonding method in power semiconductor device
　本発明は、パワー半導体素子の電極部と、それに電気的に接続すべき回路部品との間をアルミ、その他の金属のワイヤで接続する、パワー半導体装置におけるワイヤボンディング方法に関する。  The present invention relates to a wire bonding method in a power semiconductor device, in which an electrode part of a power semiconductor element and a circuit component to be electrically connected to the electrode part are connected by an aluminum or other metal wire.
　従来から、パワー半導体素子が絶縁容器内に封入されたパワー半導体装置が知られている。このようなパワー半導体装置では、半導体素子の電極部と上記回路部品との間が導電性金属ワイヤにより接続される。金属ワイヤとしては、直径が３００～５００μｍのアルミワイヤが選択されることが一般的である。ワイヤ一端部の電極部への接合に際しては、パワー半導体素子を含むワークを支持台上に所定の固定圧で固定した状態で、ウエッジツールによりワイヤ一端部を電極部に所定の押付け荷重で押付けつつ超音波振動を加え、ワイヤ一端部を電極部に一体に接合する超音波ボンディングの手法が採用されている。 Conventionally, a power semiconductor device in which a power semiconductor element is sealed in an insulating container is known. In such a power semiconductor device, the electrode portion of the semiconductor element and the circuit component are connected by a conductive metal wire. Generally, an aluminum wire having a diameter of 300 to 500 μm is selected as the metal wire. When joining one end of the wire to the electrode portion, the wire tool is pressed against the electrode portion with a predetermined pressing load with a wedge tool while the work including the power semiconductor element is fixed on the support base with a predetermined fixing pressure. An ultrasonic bonding method is adopted in which ultrasonic vibration is applied and one end of the wire is integrally bonded to the electrode portion.
　パワー半導体装置では、一般に高寿命耐量と信頼性が求められる。例えばその高寿命耐量の確認方法として、実使用時の断続的通電に即した繰り返し通電を実行して耐量評価（即ちパワーサイクル評価）が行われる。パワーサイクル評価においては、繰り返しの通電によって発生する熱によって、半導体素子とワイヤの熱膨張係数の差異とワイヤの架線形状と半導体装置の構造とに起因する熱歪がワイヤ接合部に作用する。この結果、ワイヤ接合部近傍のワイヤ内部及び接合電極内部にクラックが発生しそれが接合面の中心部側に進展して接合面が剥離することがあり、一本のワイヤの通電許容電流を超えワイヤが溶断したり、素子が破壊されたりして、回路が破断されることがある。 In general, a power semiconductor device is required to have a high life resistance and reliability. For example, as a method for confirming the long-life durability, the durability evaluation (ie, power cycle evaluation) is performed by repeatedly conducting energization in accordance with intermittent energization during actual use. In power cycle evaluation, due to heat generated by repeated energization, thermal strain caused by the difference in thermal expansion coefficient between the semiconductor element and the wire, the wire shape of the wire, and the structure of the semiconductor device acts on the wire junction. As a result, a crack may occur in the wire and the bonding electrode in the vicinity of the wire bonding portion, and the crack may propagate toward the central portion of the bonding surface and peel off, which exceeds the allowable current for one wire. The circuit may be broken by the wire being blown or the element being broken.
　そこで、上記剥離までの時間を稼ぐために接合面積を大きくしてせん断強度を得る目的で、ワイヤ径を太く、即ち５５０μｍとした技術が知られている（下記の特許文献１を参照）。 Therefore, a technique is known in which the wire diameter is increased, that is, 550 μm in order to obtain a shear strength by increasing the bonding area in order to increase the time until the peeling (see Patent Document 1 below).
　また、ワイヤを大径化すると、半導体素子に過大なウエッジ圧力が印加され、機械的ダメージを引き起こす事から、接合面積の増大に限りがあるといった点に着目し、ワイヤ径を制限するためにワイヤの接合形状を接合長さと接合幅とで規定した技術も知られている（下記の特許文献２を参照）。 Also, when the diameter of the wire is increased, an excessive wedge pressure is applied to the semiconductor element, causing mechanical damage, so that the increase in the bonding area is limited, and in order to limit the wire diameter, There is also known a technique that defines the joint shape by the joint length and the joint width (see Patent Document 2 below).
　ところで上記特許文献２の如くワイヤの接合形状を接合長さと接合幅とで特定範囲に規定した場合には、その接合形状がワイヤの長手方向に比較的長い長円形状となるが、このようにワイヤの接合形状を規定しただけでは高信頼性の半導体装置を得ることが難しい。 By the way, when the bonding shape of the wire is defined in a specific range by the bonding length and the bonding width as in Patent Document 2, the bonding shape becomes an oblong shape that is relatively long in the longitudinal direction of the wire. It is difficult to obtain a highly reliable semiconductor device simply by defining the bonding shape of the wires.
　例えば、ワイヤの接合対象である半導体素子（電極部）が傾いている場合、従来の手法では、傾きに対する許容幅が狭く、接合工程の際にウエッジツールで素子表面を傷付けたり或いは機械的に破損させてしまう可能性があり、その場合にパワー半導体装置のパワーサイクル評価（ＰＣＴ耐量）が大幅に悪化する。 For example, when the semiconductor element (electrode part) to be bonded is tilted, the conventional method has a narrow tolerance for tilting, and the surface of the element is scratched or mechanically damaged by a wedge tool during the bonding process. In this case, the power cycle evaluation (PCT tolerance) of the power semiconductor device is greatly deteriorated.
日本国特許第３０９７８８３号公報Japanese Patent No. 3097883 日本国特許第３８８２７３４号公報Japanese Patent No. 3882734
　本発明の一以上の実施形態は、ワイヤの接合面形状を円形に近づけることで、パワーサイクル評価（ＰＣＴ耐量）が高く、高信頼性のパワー半導体装置を安定よく得ることができるパワー半導体装置におけるワイヤボンディング方法を提供する。 One or more embodiments of the present invention provide a power semiconductor device that has a high power cycle evaluation (PCT withstand capability) and can stably obtain a highly reliable power semiconductor device by making the wire bonding surface shape close to a circle. A wire bonding method is provided.
　本発明の一以上の実施形態によれば、パワー半導体装置におけるワイヤボンディング方法では、パワー半導体素子Ｓを含むワークＷＫが支持台３上に所定の固定圧Ｆで固定され、横断面逆Ｖ字状のワイヤ押圧面Ｔｆを有するウエッジツールＴにより金属製ワイヤ１の一端部１ａがパワー半導体素子Ｓの電極部Ｓａに所定の押付け荷重Ｐで押付けられつつ超音波振動が加えられ、ワイヤ１の一端部１ａと電極部Ｓａとの接合面Ｊにおける接合長さＬと接合幅Ｗとの比Ｌ／Ｗが１．０～１．６の範囲となるように電極部Ｓａにワイヤ１の一端部（１ａ）が接続される。 According to one or more embodiments of the present invention, in a wire bonding method in a power semiconductor device, a work WK including a power semiconductor element S is fixed on a support base 3 with a predetermined fixing pressure F, and has an inverted V-shaped cross section. One end portion 1a of the metal wire 1 is pressed against the electrode portion Sa of the power semiconductor element S with a predetermined pressing load P by the wedge tool T having the wire pressing surface Tf. One end portion (1a of the wire 1) is connected to the electrode portion Sa so that the ratio L / W of the joining length L to the joining width W at the joining surface J of the electrode portion Sa is 1 to 1.6. ) Is connected.
　その他の特徴および効果は、実施形態の記載および添付の請求項より明白である。  Other features and effects will be apparent from the description of the embodiments and the appended claims.
典型的実施形態に係るパワーモジュールの要部断面図Sectional drawing of the principal part of the power module which concerns on typical embodiment 図１の矢印２の方向から見た平面図と、ワイヤ接合部を拡大して示す部分拡大断面図The top view seen from the direction of the arrow 2 of FIG. 1, and the partial expanded sectional view which expands and shows a wire junction part 半導体素子の電極部へワイヤ端部を接合するための超音波ボンディング工程を簡略的に説明する、図１対応の工程説明図Process explanatory drawing corresponding to FIG. 1 which demonstrates simply the ultrasonic bonding process for joining a wire edge part to the electrode part of a semiconductor element. 図３の４－４線より見た拡大端面図Enlarged end view from line 4-4 in Fig. 3 超音波ボンディングされたワイヤと素子電極との接合面に所定の通電・発熱条件で発生する歪と、接合面の比Ｌ／Ｗとの関係を、ワイヤ直径をパラメータとして実験で求めたグラフA graph of the relationship between the strain generated under predetermined energization / heating conditions on the bonding surface between the ultrasonically bonded wire and the element electrode and the ratio L / W of the bonding surface, obtained by experiment using the wire diameter as a parameter. 直径が３００μｍ、４００μｍ、５００μｍの各ワイヤを素子電極にそれぞれ超音波ボンディングしたものに関して、パワーサイクル試験で測定した耐量の変動（即ち耐久性確保のための下限目標耐量（８００００サイクル）に対する測定耐量の比率）と、接合面形状（比Ｌ／Ｗ）との関係を示すグラフFor each of the electrodes having diameters of 300 μm, 400 μm, and 500 μm that are ultrasonically bonded to the device electrodes, the variation in the tolerance measured in the power cycle test (that is, the measurement tolerance for the lower limit target tolerance (80000 cycles) for ensuring durability) Ratio) and the relationship between the joint surface shape (ratio L / W) 直径が４００μｍのワイヤ端部を素子電極にそれぞれ超音波ボンディングしたものに関して、接合面形状（比Ｌ／Ｗ）とワーク固定圧との関係を示すグラフThe graph which shows the relationship between a joining surface shape (ratio L / W) and a workpiece | work fixed pressure regarding what bonded the end part of a wire 400 micrometers in diameter to an element electrode, respectively.
　以下、本発明の典型的実施形態について、添付の図面を参照しながら説明する。 Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
　図１，図２に示すように、パワー半導体装置としてのパワーモジュールＰＭは、例えば放熱用の金属ベース板Ｂ上にはんだＨ１でマウントしたＤＣＢ基板等の絶縁回路基板Ｃと、その絶縁回路基板Ｃの上面にはんだＨ２を介して装着される複数の半導体素子Ｓとを備えている。その半導体素子Ｓとしては、例えばＩＧＢＴ、ＦＷＤあるいはＭＯＳ－ＦＥＴ等の各種素子が用いられる。 As shown in FIGS. 1 and 2, a power module PM as a power semiconductor device includes an insulated circuit board C such as a DCB board mounted on a metal base plate B for heat dissipation with solder H1, and the insulated circuit board C. And a plurality of semiconductor elements S mounted on the upper surface of the substrate via solder H2. As the semiconductor element S, various elements such as IGBT, FWD, or MOS-FET are used.
　各半導体素子Ｓの上面に露出する電極部Ｓａと、これに電気的に接続すべき図示しない他の回路部品（例えば絶縁回路基板Ｃの表面に露出した導体パターンやリードフレーム、半導体素子Ｓの周辺に設けられる主回路端子、中継端子、他の素子等）との間は、アルミよりなる複数のワイヤ１により接続される。各ワイヤ１の一端部１ａの電極部Ｓａへの接合に際しては、後述するように、ワークＷＫを支持台３に所定の固定圧Ｆで固定しながら、そのワークＷＫのワイヤ一端部１ａを電極部Ｓａに対しウエッジツールＴで所定荷重Ｐと超音波振動を加えるようにしてワイヤ一端部１ａを電極部Ｓａに圧着し、一体に接合するようにした超音波ボンディングの手法が採られる。 The electrode part Sa exposed on the upper surface of each semiconductor element S and other circuit components (not shown) to be electrically connected to the electrode part (for example, conductor patterns and lead frames exposed on the surface of the insulating circuit board C, the periphery of the semiconductor element S) Are connected to each other by a plurality of wires 1 made of aluminum. In joining the one end 1a of each wire 1 to the electrode portion Sa, as described later, while fixing the work WK to the support base 3 with a predetermined fixing pressure F, the wire one end 1a of the work WK is connected to the electrode portion. A method of ultrasonic bonding is adopted in which a predetermined load P and ultrasonic vibration are applied to Sa with a wedge tool T so that one end 1a of the wire is pressure-bonded to the electrode portion Sa and bonded together.
　次に図３，４を併せて参照して、ワイヤ一端部１ａと半導体素子Ｓの電極部Ｓａとの接合工程の一例について、具体的に説明する。なお、各ワイヤ１の他端部（図示せず）の前記回路部品への接合についても、同様の手法が採られるが、本明細書では、説明を省略する。 Next, an example of the bonding process between the wire one end 1a and the electrode part Sa of the semiconductor element S will be specifically described with reference to FIGS. In addition, although the same method is taken also about joining to the said circuit components of the other end part (not shown) of each wire 1, description is abbreviate | omitted in this specification.
　図３，４において、ウエッジツールＴは、図示しない昇降駆動装置により支持台３の上方で昇降駆動可能に支持されている。このウエッジツールＴの下端面には、ワイヤ１の長手方向（図３で左右方向）に沿って延びワイヤ１の上半部を受容し得る横断面Ｖ字状の凹溝２が形成されている。凹溝２の互いに逆方向に傾斜した左右一対の内側面が、横断面逆Ｖ字状の下向きのワイヤ押圧面Ｔｆを形成する。また前記凹溝２の底面は、該溝２の長手方向中間部においては直線状に延びているが、その長手方向両端部においては、円弧状に面取り２ｒが施されていて、この部分が超音波ボンディングの際にワイヤ１の上面に深く食い込まないようにしている。 3 and 4, the wedge tool T is supported so as to be lifted and lowered above the support base 3 by a lift drive device (not shown). On the lower end surface of the wedge tool T, a concave groove 2 having a V-shaped cross section that extends along the longitudinal direction of the wire 1 (left and right in FIG. 3) and can receive the upper half of the wire 1 is formed. . A pair of left and right inner surfaces inclined in opposite directions of the concave groove 2 form a downward wire pressing surface Tf having an inverted V-shaped cross section. The bottom surface of the concave groove 2 extends linearly in the middle portion of the groove 2 in the longitudinal direction, but both ends of the longitudinal direction are chamfered 2r in a circular arc shape. During the sonic bonding, the wire 1 is not deeply cut into the upper surface.
　超音波ボンディングを行う場合には、半導体素子Ｓを予め絶縁回路基板Ｃを介して金属ベース板Ｂ上に装着した状態（図３の状態）のワークＷＫを支持台３上に載置させると共に、クランプ装置ＣＬを以て所定の固定圧Ｆを以て固定する。そのクランプ装置ＣＬは、支持台３の側方に配設されるものであって、ワークＷＫの上部両側を上方から係合、圧接可能なクランプ腕５０と、このクランプ腕５０を昇降駆動可能に支持する駆動機構５１とを備えている。尚、図示例では、半導体素子Ｓを絶縁回路基板Ｃを介して金属ベース板Ｂ上に装着した状態（図３の状態）のワークＷＫに対し超音波ボンディングを実施するようにしたものを示したが、本発明では、例えば、単独状態の半導体素子、或いは半導体素子を絶縁回路基板上に装着しただけのもの（即ち金属ベース板には未装着状態のもの）をワークとし、それに超音波ボンディングを実施するようにしてもよい。 When performing ultrasonic bonding, the work WK in a state where the semiconductor element S is mounted on the metal base plate B via the insulating circuit board C in advance (the state shown in FIG. 3) is placed on the support base 3, and It is fixed with a predetermined fixing pressure F with the clamping device CL. The clamp device CL is disposed on the side of the support base 3 and is capable of engaging and press-contacting the upper both sides of the workpiece WK from above and driving the clamp arm 50 up and down. And a drive mechanism 51 to support the device. In the illustrated example, ultrasonic bonding is performed on the workpiece WK in a state where the semiconductor element S is mounted on the metal base plate B via the insulating circuit board C (state shown in FIG. 3). However, in the present invention, for example, a single semiconductor element or a semiconductor element that is simply mounted on an insulated circuit board (that is, a metal base plate that is not mounted) is used as a workpiece, and ultrasonic bonding is performed thereon. You may make it implement.
　ガイド手段４で中間部が案内支持されたワイヤ１の一端部１ａを半導体素子Ｓの電極部Ｓａに対応する位置まで移動させ、その電極部Ｓａを目掛けてウエッジツールＴを下降させて、そのツールＴの横断面逆Ｖ字状のワイヤ押圧面Ｔｆで、ワイヤ１の一端部１ａを上方より所定の押付け荷重Ｐ（例えばワイヤ１の直径Ｄが３００μｍの場合で４００～８００ｇｆ、また４００μｍの場合で８００～１２００ｇｆ、また５００μｍの場合で１０００～１５００ｇｆ）で押し付ける。 The one end portion 1a of the wire 1 whose intermediate portion is guided and supported by the guide means 4 is moved to a position corresponding to the electrode portion Sa of the semiconductor element S, and the wedge tool T is lowered toward the electrode portion Sa. With a wire pressing surface Tf having a reverse V-shaped cross section of the tool T, one end portion 1a of the wire 1 is pressed from above at a predetermined pressing load P (for example, when the diameter D of the wire 1 is 300 μm, 400 to 800 gf, or 400 μm) 800 to 1200 gf, and in the case of 500 μm, it is pressed at 1000 to 1500 gf).
　その荷重Ｐ及び前記固定圧Ｆを維持したまま超音波発振器（図示せず）により、ウエッジツールＴおよびワイヤ１の一端部１ａに超音波振動を作用させる。この結果、その超音波振動の摩擦によりワイヤ１の一端部１ａと電極部Ｓａとの接合面Ｊの不純物（酸化物）が除去されると共に、ワイヤ１の一端部１ａと電極部Ｓａとが固相接合され、図２，４に示すような接合形態となる。 While maintaining the load P and the fixed pressure F, ultrasonic vibration is applied to the wedge tool T and the one end 1a of the wire 1 by an ultrasonic oscillator (not shown). As a result, the impurities (oxides) on the joint surface J between the one end 1a of the wire 1 and the electrode portion Sa are removed by the friction of the ultrasonic vibration, and the one end 1a of the wire 1 and the electrode portion Sa are fixed. Phase-bonded to form a bonding configuration as shown in FIGS.
　上記接合面Ｊの平面形態は、該接合面Ｊにおける接合長さ（即ちワイヤ１の長手方向に沿う方向の長さ）をＬとし、接合幅（即ちワイヤ１を横切る方向の長さ）をＷとした場合に、Ｌを長軸とし且つＷを短軸とした概ね長円形状となる。従って、ＷがＬに近づくほど、即ちそれらの比Ｌ／Ｗが１．０に近づくほど上記接合面Ｊが円形に近づくことになる。 In the planar form of the joining surface J, the joining length (that is, the length along the longitudinal direction of the wire 1) at the joining surface J is L, and the joining width (ie, the length across the wire 1) is W. In this case, a substantially oval shape having a major axis L and a minor axis W is obtained. Therefore, the closer the W is to L, that is, the closer the ratio L / W is to 1.0, the closer the joint surface J becomes to a circle.
　前記比Ｌ／Ｗを１．０よりも低くすると、ワイヤの接合面形状がワイヤ長手方向に対し必要以上に横長となって、電極部Ｓａのワイヤの接合強度が十分に得られなくなり、また図４に示されるような接合面Ｊの横広がり部分が大きくなって、ウエッジツールＴの先端が半導体素子Ｓの表面に接触して傷付けたり破壊したりしてしまう虞れがある。従って、本発明では、比Ｌ／Ｗの下限値が１．０に定められている。 When the ratio L / W is lower than 1.0, the shape of the bonding surface of the wire becomes longer than necessary in the longitudinal direction of the wire, and the bonding strength of the wire of the electrode portion Sa cannot be obtained sufficiently. As shown in FIG. 4, the laterally spread portion of the joint surface J becomes large, and the tip of the wedge tool T may come into contact with the surface of the semiconductor element S to be damaged or destroyed. Therefore, in the present invention, the lower limit value of the ratio L / W is set to 1.0.
　実施例では、ワイヤ１として直径Ｄが３００μｍのものと、４００μｍのものと、５００μｍのものとが使用される。そのうち、直径Ｄが３００μｍのワイヤ１の端部１ａと半導体素子Ｓの電極部Ｓａとの接合面Ｊでは、その接合長さＬを３００～７５０μｍの範囲内、またその接合幅Ｗを３００～５００μｍの範囲内として、その比Ｌ／Ｗが１．０～１．５の範囲に設定される。 In the embodiment, the wire 1 has a diameter D of 300 μm, 400 μm, and 500 μm. Among them, at the joint surface J between the end portion 1a of the wire 1 having a diameter D of 300 μm and the electrode portion Sa of the semiconductor element S, the joint length L is in the range of 300 to 750 μm and the joint width W is 300 to 500 μm. The ratio L / W is set in the range of 1.0 to 1.5.
　また直径Ｄが４００μｍのワイヤ１の接合面Ｊでは、その接合長さＬを４００～１０００μｍの範囲内、またその接合幅Ｗを４００～６５０μｍの範囲内として、その比Ｌ／Ｗが１．０～１．６の範囲に設定される。 Further, at the joint surface J of the wire 1 having a diameter D of 400 μm, the joint length L is in the range of 400 to 1000 μm, the joint width W is in the range of 400 to 650 μm, and the ratio L / W is 1.0. It is set in the range of ~ 1.6.
　さらに直径Ｄが５００μｍのワイヤ１の接合面Ｊでは、その接合長さＬを５００～１２００μｍの範囲内、またその接合幅Ｗを５００～７５０μｍの範囲内として、その比Ｌ／Ｗが１．０～１．６の範囲に設定される。 Further, at the bonding surface J of the wire 1 having a diameter D of 500 μm, the bonding length L is in the range of 500 to 1200 μm and the bonding width W is in the range of 500 to 750 μm, and the ratio L / W is 1.0. It is set in the range of ~ 1.6.
　また超音波ボンディングの際のワークＷＫの支持台３への前記固定圧Ｆは、その固定圧の差異により前記接合面Ｊの形状が多少とも異なり、且つ耐量にも影響がある。このため、典型的実施形態では、０．２～１．０ＭＰａの範囲内に設定される。 Also, the fixed pressure F applied to the support 3 of the workpiece WK during ultrasonic bonding is slightly different in shape of the joint surface J due to the difference in the fixed pressure, and also has an effect on the durability. For this reason, in a typical embodiment, it is set within the range of 0.2 to 1.0 MPa.
　パワー半導体素子Ｓへのワイヤ１の超音波ボンディングの実施に関するパワーサイクル評価において、ＰＣＴ耐量に影響を与える接合面Ｊに発生する歪は、２種類ある。１つ目は、ワイヤ１と被接合面（素子電極部Ｓａ）との物性差、特に熱膨張率の差異により発生する歪である。２つ目は、通電によるワイヤ１自体の発熱で発生する、架線形状と線径に応じたワイヤ剛性に関係して発生する歪である。前者の歪は、ワイヤ１の接合面積が小さい方が発生する歪の絶対量は小さくなる。一方、後者のワイヤ剛性に関係して発生する歪は、架線方向（ワイヤ長さ方向）と平行に接合面Ｊに発生して、クラックの進展を促進させるため、接合面Ｊの接合幅Ｗが大きい場合の方が、長さ方向に発生する歪を緩和できてクラックの進展を抑制できる。しかもクラックの発生に対しては、接合面Ｊのワイヤ長手方向前後端での応力集中が過大とならないように接合面Ｊを円形とする方が長軸方向（ワイヤ長手方向）に長い扁平な楕円形とするよりも有利であって、耐量が高くなる。 In the power cycle evaluation related to the ultrasonic bonding of the wire 1 to the power semiconductor element S, there are two types of strains generated on the joint surface J that affect the PCT tolerance. The first is a strain generated due to a difference in physical properties between the wire 1 and the bonded surface (element electrode portion Sa), in particular, a difference in thermal expansion coefficient. The second is distortion generated in relation to the wire rigidity according to the shape of the overhead wire and the wire diameter, which is generated by heat generation of the wire 1 itself by energization. As for the former distortion, the absolute amount of distortion generated when the bonding area of the wire 1 is smaller becomes smaller. On the other hand, the strain generated in relation to the latter wire rigidity is generated in the joint surface J in parallel with the overhead wire direction (wire length direction) and promotes the progress of cracks. When it is larger, the strain generated in the length direction can be relaxed and the progress of cracks can be suppressed. In addition, for the occurrence of cracks, a flat ellipse that is longer in the long axis direction (longitudinal direction of the wire) when the bonding surface J is circular so that stress concentration at the front and rear ends of the bonding surface J in the longitudinal direction of the wire is not excessive. It is more advantageous than the shape, and the tolerance is increased.
　以上を検証すべく、先ず、直径Ｄが３００，４００，５００μｍの各ワイヤ１の端部１ａを半導体素子Ｓの電極部Ｓａに前述の手法で超音波ボンディングしたものにおいて、所定の通電・発熱条件で接合面Ｊに発生する歪と、接合面Ｊの比Ｌ／Ｗとの関係を実験により求め、その結果を図５に表した。この図５によれば、ワイヤ直径Ｄに関係なく比Ｌ／Ｗが小さくなればなるほど、即ち接合面Ｊの形状が円形に近づくほど発生歪が少なくなる傾向があることが判る。そして、その接合面Ｊの発生歪が接合面Ｊの耐久性（例えばＰＣＴ耐量）に直接影響を及ぼし、即ち発生歪の増大につれて耐久性は低下する傾向があることは自明であるから、図５によれば、ワイヤ直径Ｄに関係なく、比Ｌ／Ｗが小さくなればなるほど（即ち接合面Ｊの形状が円形に近づくほど）耐久性が向上する傾向が読み取れる。 In order to verify the above, first, the end portion 1a of each wire 1 having a diameter D of 300, 400, and 500 μm is ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method. The relationship between the strain generated on the joint surface J and the ratio L / W of the joint surface J was obtained by experiment, and the result is shown in FIG. According to FIG. 5, it can be seen that the smaller the ratio L / W is, regardless of the wire diameter D, that is, the distortion tends to decrease as the shape of the joint surface J approaches a circle. Then, it is obvious that the generated strain of the joint surface J directly affects the durability (for example, PCT resistance) of the joint surface J, that is, the durability tends to decrease as the generated strain increases. According to the above, regardless of the wire diameter D, it can be seen that as the ratio L / W becomes smaller (that is, the shape of the joint surface J approaches a circle), the durability tends to improve.
　次に、直径が３００，４００，５００μｍの各ワイヤ１の端部１ａを半導体素子Ｓの電極部Ｓａに前述の手法で超音波ボンディングしたものについて、所定のパワーサイクル試験を行い、その耐量（即ちＰＣＴ耐量）と前記比Ｌ／Ｗとの関係を調べて、その試験結果を図６に表した。この場合、耐量を測定するためのパワーサイクル試験として、例えば１８０～２５０Ａ程度の電流をワイヤ１を通して半導体素子Ｓに対し０．３～０．６秒ほど印加し、これを６秒程度の通電間隔で繰り返し、その後、回路の断絶（例えばワイヤの接合面からの剥離、溶融破断、半導体素子の破壊等）に至るまでの電流の通電回数を寿命、即ち耐量とする。尚、上記の通電条件は、通電により発生する半導体素子の通電前後の温度差等を指定し、決定した。 Next, a predetermined power cycle test is performed on the end portion 1a of each wire 1 having a diameter of 300, 400, and 500 μm that is ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method, and the resistance (that is, The relationship between the PCT tolerance) and the ratio L / W was examined, and the test results are shown in FIG. In this case, as a power cycle test for measuring the tolerance, for example, a current of about 180 to 250 A is applied to the semiconductor element S through the wire 1 for about 0.3 to 0.6 seconds, and this is applied for an energization interval of about 6 seconds. After that, the number of times the current is applied until the circuit is interrupted (for example, peeling from the bonding surface of the wire, melt fracture, destruction of the semiconductor element, etc.) is defined as the life, that is, withstand capability. The above energization conditions were determined by specifying a temperature difference before and after energization of the semiconductor element generated by energization.
　前記試験結果によれば、比Ｌ／Ｗが小さくなればなるほど（即ち接合面Ｊの形状が円形に近づくほど）耐量が大きくなって耐久性が高くなる傾向が確認された。自動車の推定通電時間（始動回数）相当となるように加速させた試験の耐量を、上記パワーサイクル試験では、８００００サイクルと設定している。この８００００サイクルを耐久性確保のための下限目標値として用いている。従って、図６の縦軸の数字は、耐量の下限目標値（８００００サイクル）を１として換算した指標、即ち「耐量変動」で表してある。 According to the test results, it has been confirmed that the smaller the ratio L / W is (that is, the closer the shape of the joint surface J is to a circle), the greater the resistance and the higher the durability. In the power cycle test, the tolerance of the test accelerated so as to correspond to the estimated energization time (starting frequency) of the automobile is set to 80000 cycles. This 80000 cycle is used as a lower limit target value for ensuring durability. Therefore, the numbers on the vertical axis in FIG. 6 are expressed as an index converted with the lower limit target value (80000 cycles) of the tolerable amount as 1, that is, “withstand amount fluctuation”.
　この図６に示す試験結果によれば、直径Ｄが３００μｍのワイヤ１の接合面形状における比Ｌ／Ｗの上限値は１．５となり、また直径Ｄが４００μｍのワイヤ１の接合面形状における比Ｌ／Ｗの上限値は１．６となり、さらに直径Ｄが５００μｍのワイヤ１の接合面形状における比Ｌ／Ｗの上限値も１．６となる。 According to the test results shown in FIG. 6, the upper limit value of the ratio L / W in the bonding surface shape of the wire 1 having a diameter D of 300 μm is 1.5, and the ratio in the bonding surface shape of the wire 1 having a diameter D of 400 μm. The upper limit value of L / W is 1.6, and the upper limit value of the ratio L / W in the bonding surface shape of the wire 1 having a diameter D of 500 μm is also 1.6.
　超音波ボンディング時には、前記クランプ装置ＣＬによりワークＷＫを所定の固定圧Ｆで固定することによって、ワークであるワイヤ１に効率よくボンディング時のエネルギー伝達がなされ、ワイヤ１と素子電極部Ｓａに対し必要以上に超音波の発振、加圧を加える必要が無いため、ボンディング時のエネルギーのロスを減らして効率よく接合でき、しかもボンディング時の半導体素子Ｓへの機械的ダメージを極力減らし、極力高耐量な半導体モジュールＰＭを製造することができる。この場合において、超音波振動を加える際の接合面Ｊの打点形状が楕円形のものと円形のものとでは、特にワイヤ接合形状の長手方向の傾きに対して、接合長さＬが比較的短い円形の方が接合形状の変形が小さくなって、ＰＣＴ耐量の変動が小さくなり、高信頼性の接合が得られる。 At the time of ultrasonic bonding, the work WK is fixed at a predetermined fixing pressure F by the clamping device CL, so that the energy at the time of bonding is efficiently transmitted to the wire 1 which is the work, which is necessary for the wire 1 and the element electrode portion Sa. Since there is no need to apply ultrasonic oscillation or pressure, the energy loss during bonding can be reduced and bonding can be performed efficiently, and mechanical damage to the semiconductor element S during bonding can be reduced as much as possible. The semiconductor module PM can be manufactured. In this case, the bonding length L of the bonding surface J when applying the ultrasonic vibration is relatively short with respect to the inclination in the longitudinal direction of the wire bonding shape, particularly when the hitting shape of the bonding surface J is elliptical or circular. In the circular shape, the deformation of the joint shape is reduced, the fluctuation of the PCT tolerance is reduced, and a highly reliable joint is obtained.
　また超音波ボンディング時のワーク固定圧Ｆが低い場合と高い場合とでは、同一ボンドパラメータ（ボンディングの際の加振周波数や荷重、時間）でも固定圧Ｆが低い場合の方が、接合形状が楕円形に近づき（即ち前記比Ｌ／Ｗが大きくなり）、更に同じ比Ｌ／Ｗであっても、固定圧Ｆが低い場合の方が、接合時のワイヤ構成金属の拡散量（合金層・接合層厚）が少なくなって、ＰＣＴ耐量に影響を与える真実接合面積が小さくなり、耐量が落ちる。 In addition, when the workpiece fixing pressure F during ultrasonic bonding is low and when it is high, the bonding shape is elliptical when the fixing pressure F is low even with the same bond parameters (excitation frequency, load, time during bonding). Even when the ratio is close to the shape (that is, the ratio L / W becomes larger) and the fixed ratio F is lower, the amount of diffusion of the metal constituting the wire at the time of joining (alloy layer / joining) (Layer thickness) is reduced, the actual bonding area that affects the PCT tolerance is reduced, and the tolerance is reduced.
　そこで直径Ｄが４００μｍのワイヤ１の端部１ａを半導体素子Ｓの電極部Ｓａに前述の手法で超音波ボンディングしたものについて、前記比Ｌ／Ｗと固定圧Ｆとの関係を実験により調べると、図７のグラフのようになった。尚、このグラフでは、超音波ボンディングの際のウエッジツールＴによるワイヤ押付け荷重Ｐをパラメータとしている。 Therefore, when the end portion 1a of the wire 1 having a diameter D of 400 μm is ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method, the relationship between the ratio L / W and the fixed pressure F is examined by experiment. It became like the graph of FIG. In this graph, the wire pressing load P by the wedge tool T at the time of ultrasonic bonding is used as a parameter.
　この図７の実験結果によれば、前記比Ｌ／Ｗを本発明の設定範囲である１．０～１．６に設定可能な荷重Ｐは８００ｇｆ以上の場合であり、この荷重Ｐの場合には、前記比Ｌ／Ｗを１．０～１．６に設定可能とする固定圧Ｆの設定範囲は、０．２～０．８４ＭＰａとなる。但し、固定圧Ｆの上限値（０．８４ＭＰａ）は、これを多少超えても、即ち１．０程度であれば、固定圧Ｆが大きいことに因る実害は生じないことが確認されている。このため、本発明では、直径Ｄが４００μｍのワイヤについて、前記固定圧Ｆが０．２～１．０ＭＰａに設定されることが望ましい。また、図示はしないが、直径Ｄが３００μｍ，５００μｍの各ワイヤ１の端部１ａを半導体素子Ｓの電極部Ｓａに前述の手法で超音波ボンディングしたものについても、同様の実験、解析を行ったところ、前記固定圧Ｆは０．２～１．０ＭＰａに設定されることが望ましいことが判明した。 According to the experimental results of FIG. 7, the load P that can set the ratio L / W to 1.0 to 1.6, which is the setting range of the present invention, is 800 gf or more. The setting range of the fixed pressure F that enables the ratio L / W to be set to 1.0 to 1.6 is 0.2 to 0.84 MPa. However, it is confirmed that even if the upper limit value (0.84 MPa) of the fixed pressure F exceeds a certain value, that is, about 1.0, no actual damage caused by the large fixed pressure F will occur. . Therefore, in the present invention, it is desirable that the fixed pressure F is set to 0.2 to 1.0 MPa for a wire having a diameter D of 400 μm. Further, although not shown, the same experiment and analysis were performed on the case where the end portion 1a of each wire 1 having a diameter D of 300 μm and 500 μm was ultrasonically bonded to the electrode portion Sa of the semiconductor element S by the above-described method. However, it has been found that the fixed pressure F is preferably set to 0.2 to 1.0 MPa.
　以上、典型的実施形態によれば、直径が３００～５００μｍの太さのワイヤ１の、半導体素子Ｓの電極部Ｓａへの接合面Ｊの接合長さＬと接合幅Ｗとの比Ｌ／Ｗを特定範囲に（即ち３００μｍのワイヤでは１．０～１．５に、４００及び５００μｍのワイヤでは１．０～１．６に）限定したので、その接合面Ｊの形状を可及的に円形に近づけることができる。 As described above, according to the exemplary embodiment, the ratio L / W between the bonding length L and the bonding width W of the bonding surface J of the wire 1 having a diameter of 300 to 500 μm to the electrode portion Sa of the semiconductor element S. Is limited to a specific range (ie, 1.0 to 1.5 for a 300 μm wire and 1.0 to 1.6 for 400 and 500 μm wires), the shape of the joint surface J is as circular as possible. Can be approached.
       接合面Ｊの形状を可及的に円形に近づけることにより、超音波ボンディングの接合部に発生する歪とクラックの進展を極力小さく抑制できるワイヤ接合面形状となり、しかもこのように接合面形状を円形に近づけることで接合対象（半導体素子Ｓの電極部Ｓａ）の傾きに対する許容幅を極力広げることができる。また、その傾きのために超音波ボンディング時にウエッジツールＴから半導体素子Ｓが受ける機械的ダメージを低減できるようになる。それらの結果、高耐量、高信頼性のパワー半導体モジュールＰＭを安定よく製造可能となる。 By making the shape of the joint surface J as close to a circle as possible, it becomes a wire joint surface shape that can suppress the development of strain and cracks generated at the joint part of ultrasonic bonding as small as possible, and the joint surface shape is thus circular. By approaching to, the allowable width with respect to the inclination of the object to be joined (electrode part Sa of the semiconductor element S) can be increased as much as possible. Further, due to the inclination, the mechanical damage that the semiconductor element S receives from the wedge tool T during ultrasonic bonding can be reduced. As a result, it is possible to stably manufacture a power semiconductor module PM having a high withstand capability and high reliability.
　以上、特定の実施形態および実施例について説明したが、本発明はこれらに限定されるものではなく、特許請求の範囲に記載された本発明を逸脱することなく種々の設計変更を行うことが可能である。 Although specific embodiments and examples have been described above, the present invention is not limited to these embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.
　例えば、典型的実施形態では、ワイヤをアルミ製としたものを示したが、本発明では、アルミ以外の導電性金属又は合金で形成してもよい。  For example, in the typical embodiment, the wire is made of aluminum, but in the present invention, the wire may be made of a conductive metal or alloy other than aluminum.
ＣＬ・・・・ワーククランプ装置
Ｆ・・・・・超音波ボンディングの際のワークの支持台への固定圧
Ｌ・・・・・接合長さ
Ｐ・・・・・超音波ボンディングの際にウエッジツールがワイヤ端部を押付ける荷重
ＰＭ・・・・パワー半導体装置としてのパワー半導体モジュール
Ｓ・・・・・半導体素子
Ｓａ・・・・電極部
Ｔ・・・・・ウエッジツール
Ｔｆ・・・・ワイヤ押圧面
Ｗ・・・・・接合幅
ＷＫ・・・・ワーク
１・・・・・ワイヤ
１ａ・・・・一端部 CL ··· Work clamp device F ··· Fixing pressure L to workpiece support during ultrasonic bonding · · · Joint length P · · · Wedge during ultrasonic bonding Load PM with which the tool presses the wire end ... Power semiconductor module S as a power semiconductor device ... Semiconductor element Sa ... Electrode T ... Wedge tool Tf ... Wire pressing surface W ··· Bonding width WK ··· Work piece 1 ··· Wire 1a ··· One end

Claims (6)

  1. 　パワー半導体素子（Ｓ）を含むワーク（ＷＫ）を支持台（３）上に所定の固定圧（Ｆ）で固定し、
    　横断面逆Ｖ字状のワイヤ押圧面（Ｔｆ）を有するウエッジツール（Ｔ）により、金属製ワイヤ（１）の一端部（１ａ）を前記パワー半導体素子（Ｓ）の電極部（Ｓａ）に所定の押付け荷重（Ｐ）で押付けつつ超音波振動を加え、
    　前記ワイヤ（１）の前記一端部（１ａ）と電極部（Ｓａ）との接合面（Ｊ）における接合長さ（Ｌ）と接合幅（Ｗ）との比（Ｌ／Ｗ）が１．０～１．６の範囲となるように、前記電極部（Ｓａ）に前記ワイヤ（１）の前記一端部（１ａ）を接続する、
    　ワイヤボンディング方法。     The work (WK) including the power semiconductor element (S) is fixed on the support base (3) with a predetermined fixing pressure (F),
    A wedge tool (T) having a wire pressing surface (Tf) having an inverted V-shaped cross section is used to connect one end (1a) of the metal wire (1) to the electrode portion (Sa) of the power semiconductor element (S). Apply ultrasonic vibration while pressing with the pressing load (P) of
    The ratio (L / W) of the joining length (L) to the joining width (W) at the joining surface (J) of the one end (1a) of the wire (1) and the electrode part (Sa) is 1.0. The one end (1a) of the wire (1) is connected to the electrode portion (Sa) so as to be in a range of ˜1.6.
    Wire bonding method.
  2. 　直径（Ｄ）が３００～５００μｍのワイヤ（１）を使用する、
    　請求項１に記載のワイヤボンディング方法。     Use a wire (1) with a diameter (D) of 300-500 μm,
    The wire bonding method according to claim 1.
  3. 　直径（Ｄ）が３００μｍのワイヤ（１）を使用し、
    　前記接合面（Ｊ）における前記接合長さ（Ｌ）と前記接合幅（Ｗ）との前記比（Ｌ／Ｗ）が１．０～１．５の範囲である、
    　請求項１に記載のワイヤボンディング方法。     Using a wire (1) with a diameter (D) of 300 μm,
    The ratio (L / W) between the joining length (L) and the joining width (W) in the joining surface (J) is in the range of 1.0 to 1.5.
    The wire bonding method according to claim 1.
  4. 　直径（Ｄ）が４００μｍのワイヤ（１）を使用し、
    　前記接合面（Ｊ）における前記接合長さ（Ｌ）と前記接合幅（Ｗ）との前記比（Ｌ／Ｗ）が１．０～１．６の範囲である、
    　請求項１に記載のワイヤボンディング方法。     Using a wire (1) with a diameter (D) of 400 μm,
    The ratio (L / W) between the joining length (L) and the joining width (W) in the joining surface (J) is in the range of 1.0 to 1.6.
    The wire bonding method according to claim 1.
  5. 　直径（Ｄ）が５００μｍのワイヤ（１）を使用し、
    　前記接合面（Ｊ）における前記接合長さ（Ｌ）と前記接合幅（Ｗ）との前記比（Ｌ／Ｗ）が１．０～１．６の範囲である、
    　請求項１に記載のワイヤボンディング方法。     Use a wire (1) with a diameter (D) of 500 μm,
    The ratio (L / W) between the joining length (L) and the joining width (W) in the joining surface (J) is in the range of 1.0 to 1.6.
    The wire bonding method according to claim 1.
  6. 　前記超音波ボンディングの際の前記固定圧（Ｆ）を、０．２～１．０ＭＰａの範囲内に設定する、
    　請求項１～５のいずれか１項に記載のワイヤボンディング方法。     The fixed pressure (F) at the time of the ultrasonic bonding is set within a range of 0.2 to 1.0 MPa.
    The wire bonding method according to any one of claims 1 to 5.
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JPWO2017077729A1 (en) * 2015-11-05 2017-11-02 三菱電機株式会社 Semiconductor module and manufacturing method thereof

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CN103177979A (en) * 2011-12-26 2013-06-26 富士电机株式会社 Wire bonding device, tool and main body, semiconductor device manufacturing and bonding device
JPWO2017077729A1 (en) * 2015-11-05 2017-11-02 三菱電機株式会社 Semiconductor module and manufacturing method thereof

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