JP2017163074A - Method for manufacturing power module substrate - Google Patents

Method for manufacturing power module substrate Download PDF

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JP2017163074A
JP2017163074A JP2016048023A JP2016048023A JP2017163074A JP 2017163074 A JP2017163074 A JP 2017163074A JP 2016048023 A JP2016048023 A JP 2016048023A JP 2016048023 A JP2016048023 A JP 2016048023A JP 2017163074 A JP2017163074 A JP 2017163074A
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metal layer
power module
ceramic substrate
silver
heat sink
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JP6631333B2 (en
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石塚 博弥
Hiroya Ishizuka
博弥 石塚
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Mitsubishi Materials Corp
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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
    • H01L2224/26Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321Disposition
    • H01L2224/32151Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32225Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation

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  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Abstract

PROBLEM TO BE SOLVED: To suppress increase in thermal resistance and prolong a life by securely preventing peeling at a joint interface between a metal layer made of copper or a copper alloy and a heat sink.SOLUTION: After forming a metal layer 13 by joining a metal plate made of copper or a copper alloy to a ceramic substrate 11 through an active metal brazing material containing silver, the surface of the metal layer 13 is brought into contact with a silver peeling solution to remove silver adhering to the peripheral portion of the metal layer 13, and a heat sink is soldered to the surface of the metal layer 13 opposite to the ceramic substrate 11.SELECTED DRAWING: Figure 1

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パワーモジュール用基板の製造方法に関する。   The present invention relates to a method for manufacturing a power module substrate used in a semiconductor device that controls a large current and a high voltage.

パワーモジュール基板は、セラミックス基板の一方の面に回路層が積層状態に接合され、セラミックス基板の他方の面に金属層が積層状態に接合されたものであり、その金属層にヒートシンクが接合されてヒートシンク付きパワーモジュール用基板となり、回路層に半導体チップ等の電子部品がはんだ付けされることによりパワーモジュールが構成される。   A power module substrate is a circuit board having a circuit layer bonded to one surface of a ceramic substrate, a metal layer being bonded to the other surface of the ceramic substrate, and a heat sink bonded to the metal layer. A power module substrate with a heat sink is formed, and a power module is configured by soldering an electronic component such as a semiconductor chip to the circuit layer.

特許文献1には、窒化アルミニウム(AlN)、窒化珪素(Si)等からなるセラミックス基板(絶縁基板)の両面に、銅からなる回路層及び金属層をろう材を用いて接合することが開示されている。この場合、回路層及び金属層をセラミックス基板に接合する方法として、セラミックス基板と回路層及び金属層との間にAg−Cu−Ti系ろう材の箔を挟んだ状態で、これらに荷重を加え、真空中で800〜900℃に加熱して、これらを接合状態とする活性金属法が紹介されている。また、併せて、金属層とヒートシンク(放熱体)との接合にはんだが用いられることも記載されている。 In Patent Document 1, a circuit layer and a metal layer made of copper are bonded to both surfaces of a ceramic substrate (insulating substrate) made of aluminum nitride (AlN), silicon nitride (Si 3 N 4 ) or the like using a brazing material. Is disclosed. In this case, as a method of joining the circuit layer and the metal layer to the ceramic substrate, a load is applied to the ceramic substrate and the circuit layer and the metal layer with an Ag-Cu-Ti brazing foil interposed therebetween. An active metal method in which these are heated to 800 to 900 ° C. in a vacuum to bring them into a bonded state has been introduced. In addition, it is also described that solder is used for joining the metal layer and the heat sink (heat radiator).

特開2004−221547号公報JP 2004-221547 A

しかしながら、金属層にヒートシンクをはんだ付けした場合、その後の使用環境における熱負荷によって、金属層とヒートシンクとの接合界面から剥離が生じ、パワーモジュールとしての熱抵抗が上昇してしまうという問題があった。   However, when the heat sink is soldered to the metal layer, there is a problem in that the thermal load as the power module increases due to peeling from the joint interface between the metal layer and the heat sink due to the thermal load in the subsequent use environment. .

本発明は、このような事情に鑑みてなされたものであって、銅又は銅合金からなる金属層とヒートシンクとの接合界面の剥離を確実に防止して、熱抵抗の上昇を抑制し、長寿命化を図ることができるパワーモジュール用基板の製造方法を提供することを目的とする。   The present invention has been made in view of such circumstances, and reliably prevents peeling of the bonding interface between a metal layer made of copper or a copper alloy and a heat sink, thereby suppressing an increase in thermal resistance. An object of the present invention is to provide a method for manufacturing a power module substrate capable of extending the life.

発明者は、金属層とヒートシンクとの間の剥離について鋭意研究した結果、銅又銅合金からなる金属板を活性金属ろう材を介してセラミックス基板に接合すると、加熱により溶融したろう材が金属板の側面を這い上がり、接合後の金属層の表面にろうシミとなって残存し、その上にヒートシンクがはんだ付けされると、ろうシミが生じていた部分から剥離が生じることを見出した。
そこで、ヒートシンク接合前に金属層のろうシミを除去する解決手段を採用した。
As a result of earnest research on the delamination between the metal layer and the heat sink, the inventor has joined the metal plate made of copper or copper alloy to the ceramic substrate via the active metal brazing material. It was found that when the side surface of the metal layer was crushed and remained as a solder spot on the surface of the metal layer after joining, and the heat sink was soldered thereon, peeling occurred from the part where the solder spot was generated.
Therefore, a solution for removing the solder stain on the metal layer before joining the heat sink was adopted.

すなわち、本発明のパワーモジュール用基板の製造方法は、セラミックス基板に銅又は銅合金からなる金属板を銀を含有する活性金属ろう材により接合して金属層を形成した後、前記金属層の表面を銀剥離液に接触させて、前記金属層の周縁部に付着した銀を除去する。   That is, in the method for manufacturing a power module substrate according to the present invention, a metal plate made of copper or a copper alloy is bonded to a ceramic substrate with an active metal brazing material containing silver, and then a metal layer is formed. Is brought into contact with a silver remover to remove silver adhering to the peripheral edge of the metal layer.

銀を含有する活性金属ろう材を用いて金属層とヒートシンクとを接合する場合に生じるろうシミの主成分は銀であり、銀剥離液を用いて除去することができる。銀剥離剤としては市販の銀めっき剥離剤等を用いることができる。このろうシミの銀を銀剥離剤によって除去すると、その部分の表面の銀が除去された分、凹凸が生じて表面が粗くなる。このため、その上にヒートシンクをはんだ付けすることにより、はんだ層に対するアンカー効果が期待でき、金属層とヒートシンクとの強固な接合状態を維持することができる。   The main component of the wax stain generated when the metal layer and the heat sink are joined using the active metal brazing material containing silver is silver, and can be removed using a silver stripping solution. A commercially available silver plating release agent or the like can be used as the silver release agent. When the silver of this wax stain is removed with a silver remover, the surface becomes rougher due to the removal of the silver on the surface of that portion. For this reason, by soldering the heat sink thereon, an anchor effect on the solder layer can be expected, and a strong bonding state between the metal layer and the heat sink can be maintained.

本発明のパワーモジュール用基板の製造方法において、前記銀を除去した後の前記金属層の周縁部における算術平均粗さRaを1.0μm以上5.0μm以下とするとよく、この程度の算術平均粗さとすることにより、はんだ層に対するアンカー効果を有効に発揮することができる。   In the method for manufacturing a power module substrate of the present invention, the arithmetic average roughness Ra at the peripheral edge of the metal layer after removing the silver may be 1.0 μm or more and 5.0 μm or less. By making it small, the anchor effect with respect to a solder layer can be exhibited effectively.

本発明のパワーモジュール用基板の製造方法において、前記金属層は、金属板を打ち抜き成形したものを前記セラミックス基板に積層して接合することにより形成されたものであり、打ち抜き成形時に生じるだれ面を前記セラミックス基板との接合面とは反対面に配置して前記金属板を前記セラミックス基板に接合するとよい。   In the method for manufacturing a power module substrate according to the present invention, the metal layer is formed by stacking and bonding a metal plate punched and formed on the ceramic substrate. The metal plate may be bonded to the ceramic substrate by disposing the metal plate on a surface opposite to the bonding surface with the ceramic substrate.

セラミックス基板の表面に金属層を形成する場合、銅又は銅合金からなる金属板を用意し、これをセラミックス基板の表面に積層してろう付けする。この場合、金属板は一般にプレスによる打ち抜きによって形成され、このため、金属板の一方の面の周縁部がだれ面に形成され、他方の面の周縁部にバリが生じ易い。そして、この金属板をセラミックス基板に積層する際にだれ面側をセラミックス基板に重ねると金属板が動きやすいため、バリが生じている面をセラミックス基板に重ねて接合すると強固な接合を得ることができる。しかしながら、接合時にはカーボン板の当て板によってセラミックス基板と金属板との積層体を挟み込んで荷重をかけると、金属板のだれ面の部分で当て板との間に隙間が形成され、この隙間に溶融したろう材が入り込んで金属層表面のろうシミとなる。
本発明の方法を用いることにより、金属層のだれ面における銀を除去してはんだを強固に接合することができ、打ち抜き成形した金属板とセラミックス基板との強固な接合と相俟って、長期的に信頼性の高いヒートシンク付きパワーモジュール用基板を製造することができる。
When a metal layer is formed on the surface of the ceramic substrate, a metal plate made of copper or a copper alloy is prepared, and this is laminated on the surface of the ceramic substrate and brazed. In this case, the metal plate is generally formed by punching with a press. For this reason, the peripheral portion of one surface of the metal plate is formed on the flank surface, and burrs are likely to occur on the peripheral portion of the other surface. And when laminating this metal plate on the ceramic substrate, the metal plate is easy to move if the dorsal surface side is superimposed on the ceramic substrate. Therefore, if the surface with burr is overlapped and joined to the ceramic substrate, a strong bond can be obtained. it can. However, when a load is applied by sandwiching a laminate of a ceramic substrate and a metal plate with a carbon plate contact plate during bonding, a gap is formed between the metal plate and the contact plate, and the metal melts into this gap. The brazed material enters and becomes a solder spot on the surface of the metal layer.
By using the method of the present invention, it is possible to remove the silver on the drooping surface of the metal layer and firmly bond the solder, coupled with the strong bonding between the punched metal plate and the ceramic substrate, for a long time. A highly reliable power module substrate with a heat sink can be manufactured.

本発明のヒートシンク付きパワーモジュール用基板の製造方法は、本発明の製造方法によって製造されたパワーモジュール用基板の前記金属層の前記セラミックス基板とは反対面にヒートシンクをはんだ付けする。   In the method for manufacturing a power module substrate with a heat sink according to the present invention, a heat sink is soldered to the opposite surface of the metal layer of the power module substrate manufactured by the manufacturing method according to the present invention from the ceramic substrate.

本発明によれば、銅又は銅合金からなる金属層とヒートシンクとの接合界面の剥離を確実に防止して、熱抵抗の上昇を抑制し、長寿命化を図ることができる。   ADVANTAGE OF THE INVENTION According to this invention, peeling of the joining interface of the metal layer which consists of copper or a copper alloy, and a heat sink can be prevented reliably, the raise of thermal resistance can be suppressed, and lifetime can be aimed at.

本発明の実施形態のパワーモジュール用基板の全体構成を示す縦断面図である。It is a longitudinal cross-sectional view which shows the whole structure of the board | substrate for power modules of embodiment of this invention. 図1のパワーモジュール用基板にヒートシンクをはんだ付けしてなるヒートシンク付きパワーモジュール基板の縦断面図である。It is a longitudinal cross-sectional view of the power module board | substrate with a heat sink formed by soldering a heat sink to the board | substrate for power modules of FIG. プレス成形の打ち抜きにより形成された金属板の周縁部の縦断面図である。It is a longitudinal cross-sectional view of the peripheral part of the metal plate formed by stamping of press molding. 金属板をセラミックス基板に接合している状態を示す要部の縦断面図である。It is a longitudinal cross-sectional view of the principal part which shows the state which has joined the metal plate to the ceramic substrate. 接合に用いられる加圧装置の例を示す正面図である。It is a front view which shows the example of the pressurization apparatus used for joining.

以下、本発明の実施形態を、図面を参照しながら説明する。
パワーモジュール用基板10は、図1に示すように、セラミックス基板11の一方の面に、回路層12が厚さ方向に積層された状態に接合され、セラミックス基板11の他方の面に金属層13が厚さ方向に積層された状態に接合されている。そして、金属層13にヒートシンク15が接合されることにより、図2に示すヒートシンク付きパワーモジュール用基板20が構成され、回路層12の表面にはんだ付けによって半導体素子31が搭載され、必要な配線、樹脂によるモールディングがなされることにより、パワーモジュールが構成される。
Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the power module substrate 10 is bonded to one surface of the ceramic substrate 11 in a state where the circuit layer 12 is laminated in the thickness direction, and the metal layer 13 is bonded to the other surface of the ceramic substrate 11. Are joined in a stacked state in the thickness direction. Then, the heat sink 15 is joined to the metal layer 13 to form the power module substrate 20 with a heat sink shown in FIG. 2, and the semiconductor element 31 is mounted on the surface of the circuit layer 12 by soldering, and the necessary wiring, A power module is formed by molding with resin.

セラミックス基板11は、窒化アルミニウム(AlN)、窒化珪素(Si)等により、例えば0.25mm〜1.0mmの厚さに形成される。また、回路層12及び金属層13は無酸素銅やタフピッチ銅等の銅又は銅合金により形成され、その厚さは、例えば0.1mm〜10mmとされる。
本実施形態のパワーモジュール用基板10の好ましい組合せ例としては、例えばセラミックス基板11が厚み0.32mmの窒化珪素、回路層12が厚み0.8mmの純銅板、金属層13が厚み0.8mmの純銅板で構成される。これら回路層12及び金属層13とセラミックス基板11とは銀チタン(Ag−Ti)系又は銀銅チタン(Ag−Cu−Ti)系等のろう材を用いた活性金属ろう付け法によって接合される。
The ceramic substrate 11 is formed of aluminum nitride (AlN), silicon nitride (Si 3 N 4 ), or the like to a thickness of 0.25 mm to 1.0 mm, for example. The circuit layer 12 and the metal layer 13 are made of copper or a copper alloy such as oxygen-free copper or tough pitch copper, and the thickness thereof is, for example, 0.1 mm to 10 mm.
As a preferable combination example of the power module substrate 10 of the present embodiment, for example, the ceramic substrate 11 is silicon nitride having a thickness of 0.32 mm, the circuit layer 12 is a pure copper plate having a thickness of 0.8 mm, and the metal layer 13 is having a thickness of 0.8 mm. Consists of pure copper plate. The circuit layer 12 and the metal layer 13 and the ceramic substrate 11 are joined by an active metal brazing method using a brazing material such as a silver titanium (Ag—Ti) system or a silver copper titanium (Ag—Cu—Ti) system. .

次に、このパワーモジュール用基板10及びヒートシンク付きパワーモジュール用基板20の製造方法について説明する。
この製造方法においては、まず、金属板、セラミックス基板を形成(金属板・セラミックス板形成工程)し、これらを積層状態に接合(接合工程)することによりパワーモジュール用基板10を作製し、金属層13の表面に付着した銀を除去(銀除去工程)した後、金属層13にヒートシンク15をはんだ付け(ヒートシンクはんだ付け工程)することによりヒートシンク付きパワーモジュール用基板20を作製する。
以下、この工程順に説明する。
Next, a method for manufacturing the power module substrate 10 and the power module substrate 20 with the heat sink will be described.
In this manufacturing method, first, a metal plate and a ceramic substrate are formed (metal plate / ceramic plate forming step), and these are joined in a laminated state (bonding step) to produce the power module substrate 10, and the metal layer After removing the silver adhering to the surface of 13 (silver removing step), the power module substrate 20 with a heat sink is manufactured by soldering the heat sink 15 to the metal layer 13 (heat sink soldering step).
Hereinafter, it demonstrates in order of this process.

(金属板・セラミックス基板形成工程)
銅又は銅合金からなる平板をプレス成形して、回路層12及び金属層13となる金属板17を打ち抜き加工する。この打ち抜き加工においては、プレスのパンチとダイとの間のクリアランスにより、図3に示すように、金属板17には、その一方の面(加工時にダイの成形孔に向いた面)の周縁部にだれ面17aが形成され、他方の面(成形時にパンチに押圧される面)の周縁部にバリ17bが生じ易い。
一方、セラミックス基板11は、複数個のパワーモジュール用基板10を形成できる大きさの平板を作製して、個々のパワーモジュール用基板10の大きさに分割できる溝を形成しておく。
(Metal plate / ceramic substrate formation process)
A flat plate made of copper or a copper alloy is press-molded, and the metal plate 17 to be the circuit layer 12 and the metal layer 13 is punched. In this punching process, due to the clearance between the punch of the press and the die, as shown in FIG. 3, the metal plate 17 has a peripheral portion on one surface (the surface facing the die forming hole during processing). The sagging surface 17a is formed, and the burr 17b is likely to occur at the peripheral portion of the other surface (the surface pressed by the punch during molding).
On the other hand, the ceramic substrate 11 is made of a flat plate having a size capable of forming a plurality of power module substrates 10, and grooves that can be divided into individual power module substrates 10 are formed.

(接合工程)
そして、各セラミックス基板11の領域にそれぞれ金属板17を活性金属ろう材を介して積層する。このとき、図3に示すように金属板17のだれ面17aがセラミックス基板11との接合面とは反対側に配置されるように積層する。
この積層体Sを図5に示す加圧装置によって積層方向に加圧した状態とする。
この加圧装置110は、ベース板111と、ベース板111の上面の四隅に垂直に取り付けられたガイドポスト112と、これらガイドポスト112の上端部に固定された固定板113と、これらベース板111と固定板113との間で上下移動自在にガイドポスト112に支持された押圧板114と、固定板113と押圧板114との間に設けられて押圧板114を下方に付勢するばね等の付勢手段115とを備えている。
(Joining process)
And the metal plate 17 is laminated | stacked on the area | region of each ceramic substrate 11, respectively via an active metal brazing material. At this time, as shown in FIG. 3, the metal plate 17 is laminated so that the sloping surface 17 a is disposed on the side opposite to the bonding surface with the ceramic substrate 11.
This laminated body S is in a state of being pressurized in the laminating direction by a pressurizing device shown in FIG.
The pressure device 110 includes a base plate 111, guide posts 112 vertically attached to the four corners of the upper surface of the base plate 111, a fixed plate 113 fixed to the upper ends of the guide posts 112, and the base plates 111. A pressing plate 114 supported by a guide post 112 so as to freely move up and down between the fixing plate 113 and a spring provided between the fixing plate 113 and the pressing plate 114 to urge the pressing plate 114 downward. And urging means 115.

固定板113および押圧板114は、ベース板111に対して平行に配置されており、ベース板111と押圧板114との間に前述の積層体Sが配置される。積層体Sの両面には加圧を均一にするためにクッションシート116が配設される。クッションシート116は、カーボンシートとグラファイトシートの積層板で形成されている。   The fixed plate 113 and the pressing plate 114 are arranged in parallel to the base plate 111, and the above-described laminate S is arranged between the base plate 111 and the pressing plate 114. Cushion sheets 116 are disposed on both surfaces of the laminate S to make the pressure uniform. The cushion sheet 116 is formed of a laminate of a carbon sheet and a graphite sheet.

この加圧装置110により積層体Sを加圧した状態で、加圧装置110ごと図示略の加熱炉内に設置し、真空雰囲気下で接合温度に加熱してセラミックス基板11に金属板17をろう付け接合する。この場合の接合条件としては、例えば0.05MPa以上1.0MPa以下の加圧力で、800℃以上930℃以下の接合温度で、1分〜60分の加熱とする。   In a state where the laminate S is pressurized by the pressurizing device 110, the pressurizing device 110 is installed in a heating furnace (not shown) and heated to a bonding temperature in a vacuum atmosphere to put the metal plate 17 on the ceramic substrate 11. Join. As joining conditions in this case, for example, heating is performed for 1 minute to 60 minutes at a joining temperature of 800 ° C. or more and 930 ° C. or less at a pressure of 0.05 MPa or more and 1.0 MPa or less.

このろう付けは、活性金属ろう付け法であり、ろう材中の活性金属であるTiがセラミックス基板11に優先的に拡散して窒化チタン(TiN)を形成し、銀銅(Ag−Cu)合金を介して金属板17とセラミックス基板11とを接合する。これにより、セラミックス基板11の両面に回路層12及び金属層13を接合した接合体が形成される。   This brazing is an active metal brazing method, in which Ti, which is an active metal in the brazing material, preferentially diffuses into the ceramic substrate 11 to form titanium nitride (TiN), and a silver-copper (Ag—Cu) alloy. The metal plate 17 and the ceramic substrate 11 are bonded to each other. Thereby, the joined body which joined the circuit layer 12 and the metal layer 13 on both surfaces of the ceramic substrate 11 is formed.

このようにして接合された接合体Sにおいては、金属板17とセラミックス基板11との間に介在していたろう材が金属板17の側面を伝って表面に染み出す現象が生じる。特に、前述したようにプレス成形で打抜かれた金属板17のだれ面17aがセラミックス基板11との接合面とは反対側に配置されているため、図4に示すように、加圧装置110のクッションシート116との間にだれ面17aの部分に隙間が生じており、この隙間に鎖線で示すようにろう材が侵入し易い。   In the joined body S joined in this way, a phenomenon occurs in which the brazing material interposed between the metal plate 17 and the ceramic substrate 11 oozes out to the surface along the side surface of the metal plate 17. In particular, as described above, since the drooping surface 17a of the metal plate 17 punched by press forming is disposed on the opposite side to the bonding surface with the ceramic substrate 11, as shown in FIG. A gap is formed between the cushion sheet 116 and the face 17a, and the brazing material easily enters the gap as indicated by a chain line.

(銀除去工程)
接合体を銀剥離液に浸漬させ、回路層12及び金属層13表面に付着した銀を除去する。ろう材の主成分は銀であるので、銀剥離液を用いる。
銀剥離液としては、例えば佐々木化学薬品株式会社製「エスバックAG−601」が用いられる。この「エスバックAG−601」は、酢酸及びキレート剤を主成分とした銀めっき剥離剤であり、過酸化水素水及び水とを配合した状態で用いられ、過酸化水素水で銀を酸化(イオン化)させて、キレート剤の作用で液中に円滑に溶かし出すことができる。
その好ましい配合比は、以下の通りである。
「エスバックAG−601」:1容量
35%過酸化水素水:5容量
水:4容量
この銀剥離液に接合体を適宜の時間浸漬すると、回路層12及び金属層13の周縁部に付着した銀が除去される。その結果、その周縁部が中央部分の表面に比べて粗い状態となり、回路層12及び金属層13の中央部分の表面の算術平均粗さRaが0.3μm以上0.9μm以下であるのに対して、周縁部の算術平均粗さRaが1.0μm以上5.0μm以下となる。
この場合、回路層12や金属層13の周縁部の表面粗さは、接合時のろうシミ状態に依存し、ろうシミ量が多いほど粗くなる。このため、ろうシミ量を制御すれば、銀除去工程後の表面粗さも制御することができ、金属板17とセラミックス基板11との接合面積から割り出される必要ろう材量に対する増加分を制御すればよい。
なお、この周縁部は、回路層12や金属層13の周縁からからの幅Lが0.05mm以上5mm以下の範囲である。なお、幅Lは回路層12や金属層13の周縁のダレ量によって制御することが可能である。
(Silver removal process)
The joined body is immersed in a silver stripping solution to remove silver adhering to the surface of the circuit layer 12 and the metal layer 13. Since the main component of the brazing material is silver, a silver stripping solution is used.
As the silver remover, for example, “Esvac AG-601” manufactured by Sasaki Chemical Co., Ltd. is used. This "Esback AG-601" is a silver plating stripper mainly composed of acetic acid and a chelating agent, and is used in a state where hydrogen peroxide solution and water are blended. Ionized) and can be smoothly dissolved in the liquid by the action of the chelating agent.
The preferable compounding ratio is as follows.
“Esback AG-601”: 1 volume 35% hydrogen peroxide water: 5 volumes Water: 4 volumes When the joined body was immersed in this silver stripper for an appropriate time, it adhered to the peripheral portions of the circuit layer 12 and the metal layer 13 Silver is removed. As a result, the peripheral portion becomes rougher than the surface of the central portion, and the arithmetic average roughness Ra of the surface of the central portion of the circuit layer 12 and the metal layer 13 is 0.3 μm or more and 0.9 μm or less. Thus, the arithmetic average roughness Ra of the peripheral portion is 1.0 μm or more and 5.0 μm or less.
In this case, the surface roughness of the peripheral portion of the circuit layer 12 or the metal layer 13 depends on the wax stain state at the time of bonding, and becomes rough as the amount of wax stain increases. For this reason, if the amount of soldering stains is controlled, the surface roughness after the silver removal step can be controlled, and the increase with respect to the amount of the necessary brazing material calculated from the joint area between the metal plate 17 and the ceramic substrate 11 can be controlled. That's fine.
In addition, this peripheral part is the range whose width L from the peripheral edge of the circuit layer 12 or the metal layer 13 is 0.05 mm or more and 5 mm or less. The width L can be controlled by the amount of sag at the periphery of the circuit layer 12 or the metal layer 13.

(ヒートシンクはんだ付け工程)
このようにして製造されたパワーモジュール用基板10の金属層13にヒートシンク15をはんだ付けすることにより、図2に示すヒートシンク付きパワーモジュール用基板20が形成される。このとき、ヒートシンク15は金属層13の全面にはんだ付けされる。したがって、先の銀除去工程で表面が粗くなった金属層13の周縁部にもはんだが付着して、表面の凹凸部分に侵入し、そのアンカー効果により金属層13とヒートシンク15とが強固に接合状態を維持することができる。図2において、符号18はそのはんだ接合層を示す。
(Heat sink soldering process)
The power module substrate 20 with a heat sink shown in FIG. 2 is formed by soldering the heat sink 15 to the metal layer 13 of the power module substrate 10 manufactured as described above. At this time, the heat sink 15 is soldered to the entire surface of the metal layer 13. Therefore, the solder also adheres to the peripheral portion of the metal layer 13 whose surface has been roughened in the previous silver removing step and enters the uneven portion of the surface, and the metal layer 13 and the heat sink 15 are firmly bonded by the anchor effect. The state can be maintained. In FIG. 2, the code | symbol 18 shows the solder joint layer.

以上のようにして製造されたヒートシンク付きパワーモジュール用基板20の回路層12に半導体素子31をはんだ付けし、必要な配線後に樹脂でモールディングすることにより、パワーモジュールが形成される。回路層12の周縁部の表面粗さが大きくなっているので、モールディングされた樹脂との密着性も向上する。   The power module is formed by soldering the semiconductor element 31 to the circuit layer 12 of the power module substrate 20 with a heat sink manufactured as described above, and molding it with resin after necessary wiring. Since the surface roughness of the peripheral edge of the circuit layer 12 is increased, the adhesion with the molded resin is also improved.

本発明例及び比較例のヒートシンク付きパワーモジュール用基板は、次のように製造した。40mm角で厚み0.32mmの窒化珪素からなるセラミックス基板と、37mm角で厚み0.8mmの無酸素銅からなる金属板とを用意した。なお、金属層となる金属板は、無酸素銅からなる銅板をダレ量(銅板の面方向の寸法)が表1記載の値になるようプレス加工によって得た。そして、セラミックス基板の両面にAg−27.3質量%Cu−2.0質量%Tiペーストを表1記載の厚さで塗布し、その上に金属板のバリ面を重ねるようにして、金属板とセラミックス基板とを積層し、その積層体を0.5MPaの加圧力で、870℃の温度で、30分加熱することにより接合した。
そして、接合体を水酸化ナトリウム水溶液で処理した後、水洗し、硫酸と過酸化水素の混合水溶液で洗浄処理を行った。この洗浄処理の時間によって中央部分のRaを表1の範囲内に調製した。
その接合体を前述のようにして「エスバックAG−601」で作った25℃の銀剥離液に5分間浸漬した。
この金属層の表面に、ニッケルめっきされたアルミニウム製ヒートシンク(厚み5mm)をSn‐Ag系のはんだを用いてはんだ付けし、ヒートシンク付きパワーモジュール用基板を得た。
なお、比較例1については、銀剥離液の処理を行わなかった。
そして、得られたヒートシンク付きパワーモジュール用基板について、−40℃×5分と150℃×5分との間で繰り返す冷熱サイクルを2000サイクル実施し、試験前後の金属層とヒートシンクとの接合界面を超音波探傷装置を用いて撮影し、接合率=(接合面積−非接合面積)/接合面積を求めた。
評価結果を表1に示す。
The board | substrate for power modules with a heat sink of this invention example and a comparative example was manufactured as follows. A ceramic substrate made of silicon nitride having a 40 mm square and a thickness of 0.32 mm and a metal plate made of oxygen free copper having a 37 mm square and a thickness of 0.8 mm were prepared. In addition, the metal plate used as a metal layer was obtained by press work so that the sagging amount (dimension in the surface direction of the copper plate) of the copper plate made of oxygen-free copper was a value shown in Table 1. Then, Ag-27.3 mass% Cu-2.0 mass% Ti paste was applied to both surfaces of the ceramic substrate with the thicknesses shown in Table 1, and the metal plate was overlapped with the metal plate so that And the ceramic substrate were laminated, and the laminate was joined by heating at a pressure of 0.5 MPa at a temperature of 870 ° C. for 30 minutes.
The joined body was treated with an aqueous sodium hydroxide solution, then washed with water, and washed with a mixed aqueous solution of sulfuric acid and hydrogen peroxide. The central portion Ra was adjusted within the range shown in Table 1 depending on the time of the washing treatment.
The joined body was immersed in a 25 ° C. silver stripping solution made of “Esback AG-601” as described above for 5 minutes.
A nickel-plated aluminum heat sink (thickness: 5 mm) was soldered to the surface of the metal layer using Sn-Ag solder to obtain a power module substrate with a heat sink.
In addition, about the comparative example 1, the process of the silver peeling liquid was not performed.
Then, the obtained heat module substrate with a heat sink was subjected to 2000 cycles of cooling and heating repeated between −40 ° C. × 5 minutes and 150 ° C. × 5 minutes, and the bonding interface between the metal layer and the heat sink before and after the test was performed. Images were taken using an ultrasonic flaw detector, and bonding rate = (bonding area−non-bonding area) / bonding area was determined.
The evaluation results are shown in Table 1.

表1の結果から、銀剥離液によって処理を行ったヒートシンク付きパワーモジュール用基板は、金属層とヒートシンクの接合信頼性が高いことが確認された。   From the results in Table 1, it was confirmed that the power module substrate with a heat sink treated with the silver stripping solution had high bonding reliability between the metal layer and the heat sink.

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。
実施形態では金属板、セラミックス基板接合工程後に銀除去工程によって金属層、回路層とも周縁部の銀を除去したが、本発明においては、銀除去工程は少なくとも金属層の周縁部に対して行われればよい。
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 silver in the metal layer and the circuit layer is removed from the peripheral portion by the silver removing step after the metal plate and ceramic substrate joining step, but in the present invention, the silver removing step is performed at least on the peripheral portion of the metal layer. That's fine.

10…パワーモジュール用基板
11…セラミックス基板
12…回路層
13…金属層
15…ヒートシンク、
17…金属板
17a…だれ面
17b…バリ
18…はんだ接合層
20…ヒートシンク付きパワーモジュール用基板
31…半導体素子、
110…加圧装置
116…クッションシート
DESCRIPTION OF SYMBOLS 10 ... Power module substrate 11 ... Ceramic substrate 12 ... Circuit layer 13 ... Metal layer 15 ... Heat sink,
17 ... Metal plate 17a ... Interfacing surface 17b ... Burr 18 ... Solder joint layer 20 ... Power module substrate 31 with heat sink ... Semiconductor element,
110 ... Pressure device 116 ... Cushion sheet

Claims (4)

セラミックス基板に銅又は銅合金からなる金属板を銀を含有する活性金属ろう材により接合して金属層を形成した後、前記金属層の表面を銀剥離液に接触させて、前記金属層の周縁部に付着した銀を除去することを特徴とするパワーモジュール用基板の製造方法。   After forming a metal layer by joining a metal plate made of copper or a copper alloy to a ceramic substrate with an active metal brazing material containing silver, the surface of the metal layer is brought into contact with a silver stripping solution, and the periphery of the metal layer A method for producing a power module substrate, comprising removing silver adhering to the portion. 前記銀を除去した後の前記金属層の周縁部における算術平均粗さRaを1.0μm以上5.0μm以下とすることを特徴とする請求項1記載のパワーモジュール用基板の製造方法。   2. The method for manufacturing a power module substrate according to claim 1, wherein an arithmetic average roughness Ra at a peripheral edge portion of the metal layer after removing the silver is 1.0 μm or more and 5.0 μm or less. 前記金属層は、金属板を打ち抜き成形したものを前記セラミックス基板に積層して接合することにより形成されたものであり、打ち抜き成形時に生じるだれ面を前記セラミックス基板との接合面とは反対面に配置して前記金属板を前記セラミックス基板に接合することを特徴とする請求項1又は2記載のパワーモジュール用基板の製造方法。   The metal layer is formed by stacking and bonding a metal plate punched and formed on the ceramic substrate, and a sagging surface generated at the time of punching is opposite to a surface bonded to the ceramic substrate. 3. The method for manufacturing a power module substrate according to claim 1, wherein the metal plate is disposed and bonded to the ceramic substrate. 請求項1から3のいずれか一項記載のパワーモジュール用基板の製造方法によって製造されたパワーモジュール用基板の前記金属層の前記セラミックス基板とは反対面にヒートシンクをはんだ付けすることを特徴とするヒートシンク付きパワーモジュール用基板の製造方法。   A heat sink is soldered to the surface opposite to the ceramic substrate of the metal layer of the power module substrate manufactured by the method for manufacturing a power module substrate according to any one of claims 1 to 3. Manufacturing method of power module substrate with heat sink.
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