JP2004342879A

JP2004342879A - Method of assembling thermoelectric transducing module and blazing material used for assembling the module

Info

Publication number: JP2004342879A
Application number: JP2003138476A
Authority: JP
Inventors: Yasuhiko Hori; 康彦堀; Daisuke Kusano; 大介草野; Kenichi Miyazaki; 兼一宮崎; Tomohiro Shimada; 知宏島田; Hiroyuki Kusamori; 裕之草森; Noriyuki Kudo; 徳行工藤
Original assignee: Tanaka Kikinzoku Kogyo KK; Central Research Institute of Electric Power Industry
Current assignee: Tanaka Kikinzoku Kogyo KK; Central Research Institute of Electric Power Industry
Priority date: 2003-05-16
Filing date: 2003-05-16
Publication date: 2004-12-02
Anticipated expiration: 2023-05-16
Also published as: JP4279594B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of assembling a thermoelectric transducing module by which the deterioration of a thermoelectric transducing material can be suppressed, and the thermoelectric transducing module assembled by the same; and also to provide a blazing material to be used in a bonding process in the assembling method. <P>SOLUTION: In the assembling method of the thermoelectric transducing module 10 in which a plurality of thermoelectric transducing materials are electrically connected in series via electrode members 12, has a process of bonding the electrode members 12 and thermoelectric transducing members 11 which include the thermoelectric transducing materials as constituent elements, using the blazing material, the electrode members 12 and the thermoelectric transducing members 11 are bonded together with a silver-based blazing material having a melting point of 600°C or below being interposed between the bonding surfaces of the electrode members 12 and the thermoelectric transducing members 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、熱電変換モジュールの組立方法、当該組立てに用いられるろう材および当該組立方法によって組立てられた熱電変換モジュールに関する。
【０００２】
【従来の技術】
ろう付けは、接合対象物の間にろう材を介在させた後、当該ろう材を加熱、溶融して両部材を接合する接合方法である。ろう付けで用いられるろう材は、半田などの低融点の軟ろうと、Ａｇろうなどの高融点の硬ろうとに大別できる。軟ろうは、一般的には、融点が４５０℃以下のろう材のことをいい、他方、硬ろうの多くは融点が６００℃以上のものである。電子部品をろう付けによって組立てる場合は、これらのろう材の中から、接合する部材の種類や接合形式等を考慮して、好適な材質や融点のろう材を選択して用いることになる。
【０００３】
ところで、組立ての際にろう付けが用いられている電子部品として、熱電変換モジュールがある。熱電変換モジュールは半導体部品の一種であり、熱エネルギーから電気エネルギーに、または電気エネルギーから熱エネルギーに変換する機器（デバイス）である。例えば図１に示される熱電変換モジュール１０では、ｐ型，ｎ型の２種類の半導体である熱電変換材料１１ａ（図３参照）を構成要素として有する熱電変換部材１１が用いられており、２種類の熱電変換部材１１は電極部材１２を介して交互に、そして電気的に直列に接続されている。そして、熱電変換モジュール１０では、この熱電変換部材１１と電極部材１２との接合にろう付けが用いられている。
【０００４】
熱電変換モジュールは、熱電変換部材の一方を比較的高い温度（例えば４００℃〜６００℃）にすると共に他方を相対的に低温にすると、その温度差に応じた熱起電力を発生するものである（ゼーベック効果）。また熱電変換部材に電流を流すと、熱電変換部材の一方の端部側で吸熱が生じ、他方の端部側で発熱する（ペルチェ効果）。このように、熱電変換モジュールは使用中に比較的高温になる部分を有する。そして、比較的高温の環境下で熱電変換モジュールの構造を維持するためには、熱電変換部材と電極部材との接合部が使用中に溶融することを防止する必要がある。従来、熱電変換材料と電極部材とのろう付けには、例えば、銀系の硬ろう（ＢＡｇ−１：Ａｇ４５重量％、Ｃｕ１５重量％、Ｚｎ１６重量％、Ｃｄ２４重量％、融点は６０５℃以上）などが用いられている（例えば非特許文献１参照）。
【０００５】
【非特許文献１】
日本規格協会編，ＪＩＳハンドブック溶接２００３，溶接材料，ＪＩＳ番号Ｚ−３２６１，２００３年１月発行
【０００６】
【発明が解決しようとする課題】
ところが、従来のろう付け方法では、ろう付け温度が高いことから、その熱の影響を受けて熱電変換材料が劣化することがある。劣化が生ずると、熱電変換効率が低下して発電電力が減少する。したがって、モジュール使用中の接合部の溶融を防止するにはある程度融点の高いろう材が好ましいが、熱電変換材料の劣化を考えると、より融点の高いろう材を用いることはできない。また、Ｃｄ（カドミウム）を含有するろう材を用いると、熱電変換モジュールを廃棄する際にその処理に手間がかかるという問題がある。
【０００７】
本発明は、以上のような背景の下になされたものであり、熱電変換材料の劣化が抑制される熱電変換モジュールの組立方法および当該組立方法によって組立てられた熱電変換モジュールを提供すること、当該組立方法の接合工程で用いられるろう材を提供することを課題とする。
【０００８】
【課題を解決するための手段】
本発明は、複数の熱電変換材料が電極部材を介して電気的に接続されてなる熱電変換モジュールの組立方法であり、電極部材と、前記熱電変換材料を構成要素として有する熱電変換部材とをろう材を用いて接合する工程を有する熱電変換モジュールの組立方法において、電極部材の接合面と熱電変換部材の接合面との間に、融点が６００℃以下であるＡｇ系（銀系）のろう材を介在させて接合する工程を有することを特徴とする。
【０００９】
融点が６００℃以下のろう材を用いると、接合時の加熱の影響による熱電変換材料の劣化が抑制される。劣化が抑制されると、熱電変換効率の低下が抑制されて発電電力の低下が抑えられる。したがって、本発明の組立方法で用いられる接合工程は、熱電変換部材と電極部材を接合する方法として好適である。
【００１０】
なお、熱電変換材料は、６００℃以下でゼーベック効果またはペルチェ効果を有する材料で、かつ接合に用いる銀系ろう材の融点よりも融点が高い材料である。例えば、Ｐｂ−Ｔｅ系、Ｍｎ−Ｓｉ系、Ｍｇ−Ｓｉ系、スクッテルダイト系、Ｚｎ−Ｓｂ系、ＴＡＧＳ、Ｓｉ−Ｇｅ系、Ｆｅ−Ｓｉ系、酸化物系等のものを挙げることができる。
【００１１】
ところで、ろう付けによって組立てられた一般的な電子部品は、通常、室温など１００℃以下の温度で使用されることが多いが、熱電変換モジュールは、高温側が例えば４００℃程度になっている状態で用いられるものである。このように熱電変換モジュールは特殊な条件下で使用されるものであり、熱電変換モジュール使用時に、高温側に晒された接合界面が溶融することがある。接合界面が溶融すると、電極部材や熱電変換部材が脱落するなど、熱電変換モジュールの構造を維持できなくなり、熱電変換モジュールが破壊することがある（溶融破壊）。
【００１２】
そこで、溶融破壊の防止について検討した結果、電極部材と熱電変換部材との接合用のろう材としては、融点が６００℃以下であるＡｇ−Ｃｕ−Ｓｎ系またはＡｇ−Ｃｕ−Ｉｎ系のろう材が特に好ましいことが解った。これらのろう材を用いると、熱電変換材料の劣化が最小限に抑制され、しかも溶融破壊しにくい接合部（接合界面）が得られるからである。溶融破壊しにくくなる理由であるが、ろう材が上記ろう材である場合、特に電極部材がＮｉ（ニッケル）を含む場合は、接合工程においてろう材と電極との間で液相相互拡散が生じて、合金化しやすく、接合部が再溶融温度（固相線温度）の高い金属間化合物になりやすいと考えられる。このような接合部が得られることで、モジュールが４００℃といった高温に晒されても十分な接合強度を維持できると考えられる。また、本発明に係るろう材はＣｄを含有しておらず、熱電変換モジュールの廃棄処理を含めた取扱いが容易であるという利点を有する。なお、ろう材の形態としては、ペースト状、粉末状、箔状など、種々の形態が考えられるが、上記金属間化合物や合金は硬くて加工しにくいことからペースト状が最も好ましい。ペースト状であれば作業性に優れるという利点もある。
【００１３】
Ａｇ−Ｃｕ−Ｉｎ系のろう材としては、Ａｇ：１０重量％〜７０重量％、Ｃｕ：１０重量％〜７０重量％、Ｉｎ：１０重量％〜６０重量％であるろう材（固相線が５５０℃〜５８０℃程度）が好ましく、接合時の加熱温度としては５８０℃〜６００℃が好ましい。そして、熱電変換材料の劣化をより確実に抑えることができるという点で、Ａｇ：２０重量％〜５０重量％、Ｃｕ：２０重量％〜５０重量％、Ｉｎ：２０重量％〜５０重量％であるろう材がより好ましい。
【００１４】
Ａｇ−Ｃｕ−Ｓｎ系のろう材の場合は、Ａｇ：１０重量％〜７０重量％、Ｃｕ：１０重量％〜７０重量％、Ｓｎ：１０重量％〜６０重量％であるろう材（固相線が４７０℃〜５２０℃程度）が好ましく、接合時の加熱温度としては５２０℃〜５５０℃が好ましい。そして、熱電変換材料の劣化をより確実に抑えることができるという点で、Ａｇ：３０重量％〜７０重量％、Ｃｕ：１０重量％〜４０重量％、Ｓｎ：２０重量％〜５０重量％であるろう材がより好ましい。
【００１５】
ところで、製造されたモジュールの電極部材と熱電変換部材との接合界面（接合部）について電気抵抗の検討を行ったところ、電気抵抗が大きくなる場合があることが解った。電気抵抗が大きくなる理由としては、例えば、合金層の形成や接合後の酸化等の影響が考えられる。そこで、接合界面の電気抵抗ができるだけ小さくなる接合方法について検討した。その結果、電極部材としては、Ｎｉ、Ｃｕ、Ａｇ、Ｍｏ、Ｐｔ、Ａｕ、Ｆｅ、Ｃｏ、Ｖ、Ｗ、Ｎｂ、Ｔａ、Ｐｄ、Ｉｒ、Ｚｎ、Ｉｎ、Ｃｒ、Ａｌから選択される純金属製またはこれらのうちの２種以上の金属からなる合金製が好ましかった。
【００１６】
さらに電極部材と熱電変換部材との接合界面について検討したところ、熱電変換部材としては、電極部材と接合される側の面に、Ｎｉ、Ｃｕ、Ａｇ、Ｍｏ、Ｐｔ、Ａｕ、Ｆｅ、Ｃｏ、Ｖ、Ｗ、Ｎｂ、Ｔａ、Ｐｄ、Ｉｒ、Ｚｎ、Ｉｎ、Ｃｒ、Ａｌから選択される純金属またはこれらのうちの２種以上の金属からなる合金がメタライズされた層を有する熱電変換部材が好ましかった。
【００１７】
なお、メタライズによる金属層の構成としては、熱電変換材料に上記金属または合金の層を１層形成する構成だけでなく、２層以上形成する構成も含まれる。例えば熱電変換部材においてＰｂ−Ｔｅ系の熱電変換材料を用い、当該熱電変換材料に金属層を２層以上形成する場合であれば、熱電変換材料に直接形成する第一層としてはＦｅ（鉄）またはＦｅを含有する合金が好ましい。第一層の金属をＦｅまたはＦｅ含有合金にすると、Ｐｂ−Ｔｅ系の熱電変換材料が構成要素として用いられた熱電変換部材と電極部材との接合部の電気抵抗の増大が最小限に抑制されて発電電力の低下が抑制されるなど、熱電変換モジュール特性が向上する。
【００１８】
メタライズとは、上記金属を熱電変換材料の表面に接合・接着することであり、その方法としては、ホットプレス法（ＨＰ法）、プリント法、めっき、溶射または放電プラズマ焼結法（ＳＰＳ法）、物理的蒸着法（ＰＶＤ法）、化学的蒸着法（ＣＶＤ法）など種々の方法がある。
【００１９】
また、熱電変換モジュールの組立方法について検討する中で、次のようなろう材に関する発明を想到するに至った。
【００２０】
すなわち、複数の熱電変換材料が電極部材を介して電気的に接続されてなる熱電変換モジュール組立用のろう材であって、融点（固相線温度）が６００℃以下であり、溶融後に得られる合金の４００℃〜５００℃におけるビッカース硬さ（ＨＶ）が１００〜２００である熱電変換モジュール組立用のろう材である。
【００２１】
このようなろう材を用いれば、６００℃以下のろう付け温度で電極部材と熱電変換部材とを接合できるので、接合時の熱の影響による熱電変換材料の劣化が最小限に抑制される。劣化が抑制されると、熱電変換効率の低下が抑制されて発電電力の減少が抑えられる。そして、上記所定温度におけるビッカース硬さ（ＨＶ）が１００〜２００である強固な接合部を有する熱電変換モジュールを製造できる。したがって、熱電変換モジュール使用時に接合部が高温になっても接合部（接合界面）における溶融破壊が防止される。熱電変換モジュール使用時の溶融破壊を防止できれば、電極部材や熱電変換部材の脱落が防止され、熱電変換モジュールの構造が確実に維持される。また、Ｃｄを含有していないので熱電変換モジュールの廃棄処理を含めた取扱いが容易である。
【００２２】
上述した特性を有するろう材としては、Ａｇ−Ｃｕ−Ｓｎ系またはＡｇ−Ｃｕ−Ｉｎ系のろう材が好ましい。そして、より具体的には、Ａｇ−Ｃｕ−Ｉｎ系のろう材としては、Ａｇ：１０重量％〜７０重量％、Ｃｕ：１０重量％〜７０重量％、Ｉｎ：１０重量％〜６０重量％であるろう材が好ましく、熱電変換材料の劣化およびモジュール使用時の溶融破壊をより確実に防止できるという点で、Ａｇ：２０重量％〜５０重量％、Ｃｕ：２０重量％〜５０重量％、Ｉｎ：２０重量％〜５０重量％であるろう材がより好ましい。
【００２３】
また、Ａｇ−Ｃｕ−Ｓｎ系のろう材の場合は、より具体的には、Ａｇ：１０重量％〜７０重量％、Ｃｕ：１０重量％〜７０重量％、Ｓｎ：１０重量％〜６０重量％であるろう材が好ましく、熱電変換材料の劣化およびモジュール使用時の溶融破壊をより確実に防止できるという点で、Ａｇ：３０重量％〜７０重量％、Ｃｕ：１０重量％〜４０重量％、Ｓｎ：２０重量％〜５０重量％であるろう材がより好ましい。
【００２４】
【発明の実施の形態】
本発明に係る熱電変換モジュールの組立方法およびろう材の好適な実施形態を説明する。
【００２５】
組立ての対象である熱電変換モジュール１０は、概略的には、図１に示されるように、熱電変換材料１１ａ（図２参照）を構成要素として含む熱電変換部材１１を電極部材１２で挟んだ構造である。熱電変換材料は、Ｐｂ−Ｔｅ系の半導体であり、ｎ型およびｐ型の２種類がある。この熱電変換モジュール１０では、ｎ型の熱電変換材料１１ａを含む熱電変換部材１１と、ｐ型の熱電変換材料１１ａを含む熱電変換部材１１とが、ニッケル（Ｎｉ）製の電極部材１２を介して交互に、電気的に直列に接続されている。そして、熱電変換部材１１相互の接続部（すなわち電極部材１２）が熱電変換部材１１の一方側（例えば高温側）と他方側（例えば低温側）に交互に位置する構造になっている。なお、符号「１３」はろう付けまたは溶接によって電極部材１２に接合された導電用のリード線である。
【００２６】
このような熱電変換モジュールの組立てについて説明する。
【００２７】
まず、ある程度の大きさを有する板状の熱電変換材料（不図示）の両端にメタライズする金属を積層し、放電プラズマ焼結法（ＳＰＳ法）による一体焼結によって焼結体を得た。熱電変換材料は、Ｐｂ−Ｔｅ系であり、積層した金属は第１層（熱電変換材料側）が鉄（Ｆｅ）、第２層がニッケル（Ｎｉ）であった。次に、得られた焼結体を切断して、図２に示されるように、両端に鉄１１ｂおよびニッケル１１ｃが積層状態でメタライズされた熱電変換部材１１（５ｍｍ×５ｍｍ×９ｍｍ）を得た。また、大きさが６ｍｍ×１２ｍｍ×１ｍｍのニッケル製の電極部材１２を用意した。そして、熱電変換部材１１と電極部材１２との間にろう材１４を介在させて（図３参照）、１００％水素雰囲気でろう付けを行い、熱電変換モジュール１０を製造した。
【００２８】
実施例１〜実施例３
これらの実施例では、熱電変換部材１１と電極部材１２とを接合するためのろう材１４として、ペースト状のＡｇ−Ｃｕ−Ｉｎろう材を用いた。ペースト状のろう材は、ＡｇとＣｕとＩｎの合金にアトマイズ法を適用して得た粉末状のＡｇ−Ｃｕ−Ｉｎろう材と、エタノール系溶媒と、アクリル樹脂とを混合して得たものである。ろう材の組成、ろう付け時の加熱温度条件を表１に示す。
【００２９】
実施例４〜実施例６
これらの実施例では、熱電変換部材１１と電極部材１２とを接合するろう材１４としてＡｇ−Ｃｕ−Ｓｎろう材を用いて熱電変換モジュールを組立てた。なお、ろう付け時の加熱温度条件は５５０℃であった。これら以外の条件は、実施例１と同じであったので説明を省略する。
【００３０】
比較例１：ろう材１４として、ＢＡｇ−１（Ａｇ４５重量％、Ｃｕ１５重量％、Ｚｎ１６重量％、Ｃｄ２４重量％、融点は６０５℃以上）を用いた（非特許文献１参照）。また、ろう付け時の加熱温度条件を表１に示す。これ以外の条件は、実施例１と同じであった。
【００３１】
製造された熱電変換モジュールについて、接合部の高温状態での硬さを測定した。硬さ測定では、熱電変換部材と電極部材との接合部を４５０℃に加熱し、この状態で接合部のビッカース硬さ（ＨＶ）を測定した。測定結果を表１に示す。また、製造された熱電変換モジュールの発電電力およびモジュール全体の電気抵抗に占める接合部の電気抵抗の割合等を測定した。発電電力の測定では、高温側を５００℃に、そして低温側を６５℃にして発電電力を測定した。また、モジュール全体および接合部の電気抵抗の測定では、直流一探針法によって、モジュール全体の電気抵抗分布および接合部の電気抵抗を測定して、全電気抵抗に占める接合部の電気抵抗の割合を求めた。
【００３２】
【表１】

【００３３】
表１に示されるように、比較例１の熱電変換モジュールでは接合部の硬さを維持できなかったが、各実施例の熱電変換モジュールの接合部は、４５０℃に加熱された状態で、ビッカース硬さ（ＨＶ）が１５０以上であった。このような硬さを有していれば熱電変換モジュールとして必要な強度が確保され、溶融破壊が防止されると判断される。例えば中温域で使用される熱電変換モジュールは、高温側が４００℃以上（４００℃〜５００℃）に加熱された状態で用いられるが、実施例の熱電変換モジュールの接合部はこのような使用状態においても強度を有することが解った。なお、５００℃に加熱した状態においても硬さ（ＨＶで１００以上）を有していた。このように、高温状態でも硬さを有するのは、上述したように接合部に高融点の金属間化合物が形成されるからであると考えられる。また、ろう付けによってメタライズ金属や電極部材の一部がろう材と合金化することが硬さ確保に寄与していると考えられる。
【００３４】
また、実施例１の熱電変換モジュールについて発電電力を測定したところ、０．８４Ｗ（０．２９Ｖ，２．９Ａ）という０．８Ｗ以上の発電電力が確認された。さらに、実施例１の熱電変換モジュールについて、熱電部材を構成する熱電変換材料の抵抗を測定した。その結果、ｐ型素子の場合、接合前が３９．７×１０^−６Ω／ｍｍ^２、接合後が４２．８×１０^−６Ω／ｍｍ^２、そしてｎ型素子の場合、接合前が３１．３×１０^−６Ω／ｍｍ^２、接合後が３１．４×１０^−６Ω／ｍｍ^２であった。これらの結果は接合時の加熱条件が同じである各実施例にも当てはまると考えられる。このように、本実施形態のモジュールの組立方法を用いると、熱電変換材料の劣化が最小限に抑制された。
【００３５】
また、実施例１の熱電変換モジュールについて全電気抵抗に占める接合部の電気抵抗の割合を測定したところ、その割合は１．０％程度またはそれ以下であった。このように、本実施形態の組立方法によれば、接合部の電気抵抗を小さい値に抑制された。
【００３６】
【発明の効果】
以上のように、本発明に係る熱電変換モジュールの組立方法やろう材を用いれば、接合時の熱の影響による熱電変換材料の劣化が最小限に抑制され、発電電力の低下が最小限に抑制される。そして、熱電変換モジュール使用時の接合界面の溶融破壊が防止される。溶融破壊が防止されると、電極部材や熱電変換部材の脱落が防止され、熱電変換モジュールの構造が確実に維持される。
【図面の簡単な説明】
【図１】熱電変換モジュールを示す斜視図。
【図２】熱電変換材料の両端面に鉄、ニッケルがメタライズされた熱電変換部材を示す正面図。
【図３】熱電変換モジュール製造時の接合構造を示す側面図。
【符号の説明】
１０熱電変換モジュール
１１熱電変換部材
１１ａ熱電変換材料
１２電極部材
１４ろう材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of assembling a thermoelectric conversion module, a brazing material used for the assembling, and a thermoelectric conversion module assembled by the assembling method.
[0002]
[Prior art]
Brazing is a joining method in which, after a brazing material is interposed between objects to be joined, the brazing material is heated and melted to join both members. The brazing material used in brazing can be broadly classified into a low melting point soft solder such as solder and a high melting point hard solder such as Ag brazing. Soft solder generally refers to a brazing material having a melting point of 450 ° C. or less, while many hard solders have a melting point of 600 ° C. or more. When assembling an electronic component by brazing, a suitable material and a brazing material having a melting point are selected from these brazing materials in consideration of the type of the member to be joined, the joining type, and the like.
[0003]
By the way, there is a thermoelectric conversion module as an electronic component in which brazing is used at the time of assembly. A thermoelectric conversion module is a type of semiconductor component, and is a device that converts heat energy to electric energy or vice versa. For example, in the thermoelectric conversion module 10 shown in FIG. 1, a thermoelectric conversion member 11 having thermoelectric conversion materials 11a (see FIG. 3), which are two types of semiconductors of p-type and n-type, is used. Are electrically connected alternately and electrically in series via electrode members 12. In the thermoelectric conversion module 10, brazing is used for joining the thermoelectric conversion member 11 and the electrode member 12.
[0004]
The thermoelectric conversion module generates a thermoelectromotive force according to the temperature difference when one of the thermoelectric conversion members is set at a relatively high temperature (for example, 400 ° C. to 600 ° C.) and the other is set at a relatively low temperature. (Seebeck effect). In addition, when a current flows through the thermoelectric conversion member, heat is absorbed at one end of the thermoelectric conversion member and heat is generated at the other end (Peltier effect). Thus, the thermoelectric conversion module has a portion that becomes relatively hot during use. Then, in order to maintain the structure of the thermoelectric conversion module under a relatively high temperature environment, it is necessary to prevent the junction between the thermoelectric conversion member and the electrode member from melting during use. Conventionally, for brazing a thermoelectric conversion material to an electrode member, for example, a silver-based hard solder (BAg-1: Ag 45% by weight, Cu 15% by weight, Zn 16% by weight, Cd 24% by weight, melting point: 605 ° C. or more) (For example, see Non-Patent Document 1).
[0005]
[Non-patent document 1]
Japan Standards Association, JIS Handbook Welding 2003, Welding Materials, JIS No. Z-3261, published in January 2003
[Problems to be solved by the invention]
However, in the conventional brazing method, since the brazing temperature is high, the thermoelectric conversion material may be deteriorated under the influence of the heat. When the deterioration occurs, the thermoelectric conversion efficiency decreases and the generated power decreases. Therefore, a brazing filler metal having a relatively high melting point is preferable to prevent melting of the joint during use of the module. However, considering the deterioration of the thermoelectric conversion material, a brazing filler metal having a higher melting point cannot be used. In addition, when a brazing material containing Cd (cadmium) is used, there is a problem that when the thermoelectric conversion module is discarded, it takes time to process the module.
[0007]
The present invention has been made under the above background, and provides a method for assembling a thermoelectric conversion module in which deterioration of a thermoelectric conversion material is suppressed and a thermoelectric conversion module assembled by the assembling method. It is an object to provide a brazing material used in a joining step of an assembling method.
[0008]
[Means for Solving the Problems]
The present invention is a method for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected via electrode members, and includes an electrode member and a thermoelectric conversion member having the thermoelectric conversion material as a constituent element. In the method for assembling a thermoelectric conversion module including a step of joining using a material, an Ag-based (silver-based) brazing material having a melting point of 600 ° C. or less is provided between the joining surface of the electrode member and the joining surface of the thermoelectric conversion member. And a step of joining with interposing.
[0009]
When a brazing material having a melting point of 600 ° C. or less is used, deterioration of the thermoelectric conversion material due to the influence of heating during joining is suppressed. When the deterioration is suppressed, a decrease in thermoelectric conversion efficiency is suppressed, and a decrease in generated power is suppressed. Therefore, the joining step used in the assembling method of the present invention is suitable as a method for joining the thermoelectric conversion member and the electrode member.
[0010]
The thermoelectric conversion material is a material having a Seebeck effect or a Peltier effect at 600 ° C. or lower and having a melting point higher than the melting point of the silver brazing material used for bonding. For example, Pb-Te-based, Mn-Si-based, Mg-Si-based, skutterudite-based, Zn-Sb-based, TAGS, Si-Ge-based, Fe-Si-based, and oxide-based ones can be used. .
[0011]
By the way, a general electronic component assembled by brazing is usually used at a temperature of 100 ° C. or less, such as room temperature, but a thermoelectric conversion module has a high temperature side of, for example, about 400 ° C. What is used. As described above, the thermoelectric conversion module is used under special conditions, and when the thermoelectric conversion module is used, the bonding interface exposed to the high-temperature side may melt. When the bonding interface is melted, the structure of the thermoelectric conversion module cannot be maintained, for example, the electrode member or the thermoelectric conversion member falls off, and the thermoelectric conversion module may be broken (melting failure).
[0012]
Therefore, as a result of studying the prevention of melt fracture, as a brazing material for joining the electrode member and the thermoelectric conversion member, an Ag-Cu-Sn-based or Ag-Cu-In-based brazing material having a melting point of 600 ° C or less is used. Was found to be particularly preferred. If these brazing materials are used, deterioration of the thermoelectric conversion material is suppressed to a minimum, and a joint (joint interface) that is not easily melted and broken can be obtained. This is the reason why it is difficult to cause melt fracture. When the brazing material is the above brazing material, particularly when the electrode member contains Ni (nickel), liquid phase mutual diffusion occurs between the brazing material and the electrode in the joining step. Therefore, it is considered that the alloy is easy to be alloyed and the joint is likely to be an intermetallic compound having a high remelting temperature (solidus temperature). It is considered that by obtaining such a joint, a sufficient joint strength can be maintained even when the module is exposed to a high temperature such as 400 ° C. Further, the brazing material according to the present invention does not contain Cd, and has an advantage that handling including disposal of the thermoelectric conversion module is easy. Various forms such as a paste, a powder, and a foil can be considered as the form of the brazing material, but the above-mentioned intermetallic compound and alloy are most preferably paste because they are hard and difficult to process. There is also an advantage that the workability is excellent if the paste is used.
[0013]
Examples of the Ag-Cu-In-based brazing material include a brazing material containing 10% to 70% by weight of Ag, 10% to 70% by weight of Cu, and 10% to 60% by weight of In (550 ° C. to 580 ° C.), and the heating temperature at the time of joining is preferably 580 ° C. to 600 ° C. In addition, Ag: 20% by weight to 50% by weight, Cu: 20% by weight to 50% by weight, In: 20% by weight to 50% by weight from the viewpoint that deterioration of the thermoelectric conversion material can be suppressed more reliably. Brazing material is more preferred.
[0014]
In the case of an Ag-Cu-Sn-based brazing material, a brazing material containing 10% to 70% by weight of Ag, 10% to 70% by weight of Cu, and 10% to 60% by weight of Sn (solidus wire). Is about 470 ° C. to 520 ° C.), and the heating temperature at the time of bonding is preferably 520 ° C. to 550 ° C. Then, from the viewpoint that deterioration of the thermoelectric conversion material can be suppressed more reliably, Ag: 30% by weight to 70% by weight, Cu: 10% by weight to 40% by weight, and Sn: 20% by weight to 50% by weight. Brazing material is more preferred.
[0015]
By the way, when the electric resistance was examined for the joint interface (joint portion) between the electrode member and the thermoelectric conversion member of the manufactured module, it was found that the electric resistance sometimes increased. The reason why the electric resistance is increased may be, for example, the influence of formation of an alloy layer, oxidation after joining, or the like. Therefore, a joining method that minimizes the electric resistance at the joining interface was examined. As a result, the electrode member is made of pure metal selected from Ni, Cu, Ag, Mo, Pt, Au, Fe, Co, V, W, Nb, Ta, Pd, Ir, Zn, In, Cr, and Al. Alternatively, an alloy made of two or more of these metals was preferred.
[0016]
Further, the bonding interface between the electrode member and the thermoelectric conversion member was examined. As a thermoelectric conversion member, Ni, Cu, Ag, Mo, Pt, Au, Fe, Co, V , W, Nb, Ta, Pd, Ir, Zn, In, Cr, Al, or a thermoelectric conversion member having a layer metallized with an alloy of two or more of these metals is preferred. won.
[0017]
The configuration of the metal layer by metallization includes not only a configuration in which one layer of the metal or alloy is formed on the thermoelectric conversion material, but also a configuration in which two or more layers are formed. For example, if a thermoelectric conversion member of a Pb-Te type is used in the thermoelectric conversion member and two or more metal layers are formed on the thermoelectric conversion material, the first layer directly formed on the thermoelectric conversion material is Fe (iron). Alternatively, an alloy containing Fe is preferable. When the first layer metal is Fe or an alloy containing Fe, an increase in the electrical resistance at the junction between the thermoelectric conversion member and the electrode member using a Pb-Te-based thermoelectric conversion material as a component is suppressed to a minimum. As a result, the characteristics of the thermoelectric conversion module are improved, for example, a decrease in generated power is suppressed.
[0018]
Metallization means joining and bonding the above metal to the surface of a thermoelectric conversion material. The method includes hot pressing (HP), printing, plating, thermal spraying or spark plasma sintering (SPS). There are various methods such as a physical vapor deposition method (PVD method) and a chemical vapor deposition method (CVD method).
[0019]
In addition, while studying a method of assembling the thermoelectric conversion module, the inventors have come up with the following invention relating to brazing material.
[0020]
That is, it is a brazing material for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected via electrode members, and has a melting point (solidus temperature) of 600 ° C. or less and is obtained after melting. A brazing material for assembling a thermoelectric conversion module having a Vickers hardness (HV) of 100 to 200 at 400 ° C to 500 ° C of an alloy.
[0021]
When such a brazing material is used, the electrode member and the thermoelectric conversion member can be joined at a brazing temperature of 600 ° C. or less, so that deterioration of the thermoelectric conversion material due to the influence of heat at the time of joining is minimized. When the deterioration is suppressed, the decrease in the thermoelectric conversion efficiency is suppressed, and the decrease in the generated power is suppressed. Then, a thermoelectric conversion module having a strong joint having a Vickers hardness (HV) of 100 to 200 at the predetermined temperature can be manufactured. Therefore, even when the temperature of the joint becomes high when the thermoelectric conversion module is used, the melt fracture at the joint (joining interface) is prevented. If melting and destruction during use of the thermoelectric conversion module can be prevented, the electrode member and the thermoelectric conversion member are prevented from falling off, and the structure of the thermoelectric conversion module is reliably maintained. Further, since Cd is not contained, handling including disposal of the thermoelectric conversion module is easy.
[0022]
As the brazing material having the above-described characteristics, an Ag-Cu-Sn-based or Ag-Cu-In-based brazing material is preferable. More specifically, as the Ag-Cu-In-based brazing material, Ag: 10% by weight to 70% by weight, Cu: 10% by weight to 70% by weight, In: 10% by weight to 60% by weight. Certain brazing materials are preferred and Ag: 20% to 50% by weight, Cu: 20% to 50% by weight, In: In terms of being able to more reliably prevent deterioration of the thermoelectric conversion material and melt fracture during module use, In: More preferably, the brazing material is 20% to 50% by weight.
[0023]
In the case of an Ag-Cu-Sn brazing material, more specifically, Ag: 10% by weight to 70% by weight, Cu: 10% by weight to 70% by weight, Sn: 10% by weight to 60% by weight Is preferred, and from the viewpoint that deterioration of the thermoelectric conversion material and melting fracture during use of the module can be more reliably prevented, Ag: 30% by weight to 70% by weight, Cu: 10% by weight to 40% by weight, Sn : More preferred is a brazing filler metal of 20% by weight to 50% by weight.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of a method for assembling a thermoelectric conversion module and a brazing material according to the present invention will be described.
[0025]
The thermoelectric conversion module 10 to be assembled has a structure in which a thermoelectric conversion member 11 including a thermoelectric conversion material 11a (see FIG. 2) as a component is sandwiched between electrode members 12, as shown in FIG. It is. The thermoelectric conversion material is a Pb-Te-based semiconductor, and has two types of n-type and p-type. In the thermoelectric conversion module 10, the thermoelectric conversion member 11 including the n-type thermoelectric conversion material 11a and the thermoelectric conversion member 11 including the p-type thermoelectric conversion material 11a are interposed through the nickel (Ni) electrode member 12. Alternately, they are electrically connected in series. Then, the connecting portions (that is, the electrode members 12) of the thermoelectric conversion members 11 are alternately positioned on one side (for example, high temperature side) and the other side (for example, low temperature side) of the thermoelectric conversion members 11. Reference numeral “13” is a conductive lead wire joined to the electrode member 12 by brazing or welding.
[0026]
The assembly of such a thermoelectric conversion module will be described.
[0027]
First, a metal to be metallized was laminated on both ends of a plate-like thermoelectric conversion material (not shown) having a certain size, and a sintered body was obtained by integral sintering by a discharge plasma sintering method (SPS method). The thermoelectric conversion material was a Pb-Te-based material, and the laminated metal had a first layer (thermoelectric conversion material side) of iron (Fe) and a second layer of nickel (Ni). Next, the obtained sintered body was cut to obtain a thermoelectric conversion member 11 (5 mm × 5 mm × 9 mm) in which iron 11 b and nickel 11 c were metallized in a laminated state at both ends, as shown in FIG. . Further, a nickel electrode member 12 having a size of 6 mm × 12 mm × 1 mm was prepared. Then, the brazing material 14 was interposed between the thermoelectric conversion member 11 and the electrode member 12 (see FIG. 3), and brazing was performed in a 100% hydrogen atmosphere to manufacture the thermoelectric conversion module 10.
[0028]
Example 1 to Example 3
In these examples, a paste Ag-Cu-In brazing material was used as the brazing material 14 for joining the thermoelectric conversion member 11 and the electrode member 12. The paste brazing material is obtained by mixing a powdery Ag-Cu-In brazing material obtained by applying an atomizing method to an alloy of Ag, Cu, and In, an ethanol-based solvent, and an acrylic resin. It is. Table 1 shows the composition of the brazing material and the heating temperature conditions during brazing.
[0029]
Example 4 to Example 6
In these examples, a thermoelectric conversion module was assembled using an Ag-Cu-Sn brazing material as the brazing material 14 for joining the thermoelectric conversion member 11 and the electrode member 12. The heating temperature condition at the time of brazing was 550 ° C. The other conditions were the same as those of the first embodiment, and the description is omitted.
[0030]
Comparative Example 1 : BAg-1 (Ag 45% by weight, Cu 15% by weight, Zn 16% by weight, Cd 24% by weight, melting point of 605 ° C. or more) was used as the brazing material 14 (see Non-Patent Document 1). Table 1 shows the heating temperature conditions during brazing. Other conditions were the same as in Example 1.
[0031]
About the manufactured thermoelectric conversion module, the hardness in the high temperature state of the joining part was measured. In the hardness measurement, the joint between the thermoelectric conversion member and the electrode member was heated to 450 ° C., and in this state, the Vickers hardness (HV) of the joint was measured. Table 1 shows the measurement results. In addition, the ratio of the electrical resistance of the junction to the electrical power generated by the manufactured thermoelectric conversion module and the electrical resistance of the entire module was measured. In the measurement of the generated power, the generated power was measured at 500 ° C. on the high temperature side and at 65 ° C. on the low temperature side. In the measurement of the electric resistance of the entire module and the joint, the distribution of electric resistance of the entire module and the electric resistance of the joint are measured by a direct current probe method, and the ratio of the electric resistance of the joint to the total electric resistance is measured. I asked.
[0032]
[Table 1]

[0033]
As shown in Table 1, although the thermoelectric conversion module of Comparative Example 1 could not maintain the hardness of the joint, the thermoelectric conversion module of each example had a Vickers joint heated to 450 ° C. Hardness (HV) was 150 or more. If it has such hardness, it is determined that the strength required for the thermoelectric conversion module is secured, and that the melt fracture is prevented. For example, a thermoelectric conversion module used in a medium temperature range is used in a state where the high temperature side is heated to 400 ° C. or more (400 ° C. to 500 ° C.). Was also found to have strength. In addition, even if it heated at 500 degreeC, it had hardness (100 or more in HV). As described above, it is considered that the reason why the alloy has hardness even in a high temperature state is that a high melting point intermetallic compound is formed at the joint as described above. In addition, it is considered that the alloying of the metallized metal and the electrode member with the brazing material by brazing contributes to securing the hardness.
[0034]
Further, when the generated power of the thermoelectric conversion module of Example 1 was measured, the generated power of 0.84 W (0.29 V, 2.9 A) of 0.8 W or more was confirmed. Further, for the thermoelectric conversion module of Example 1, the resistance of the thermoelectric conversion material constituting the thermoelectric member was measured. As a result, in the case of the p-type element, 39.7 × 10 ⁻⁶ Ω / mm ² before bonding, 42.8 × 10 ⁻⁶ Ω / mm ² after bonding, and in the case of n-type element, 31 before bonding. 0.3 × 10 ⁻⁶ Ω / mm ² , and 31.4 × 10 ⁻⁶ Ω / mm ² after bonding. It is considered that these results also apply to each of the examples in which the heating conditions during bonding are the same. As described above, when the module assembling method of the present embodiment was used, the deterioration of the thermoelectric conversion material was minimized.
[0035]
In addition, when the ratio of the electric resistance of the junction to the total electric resistance of the thermoelectric conversion module of Example 1 was measured, the ratio was about 1.0% or less. As described above, according to the assembling method of the present embodiment, the electric resistance of the joint is suppressed to a small value.
[0036]
【The invention's effect】
As described above, if the method for assembling the thermoelectric conversion module and the brazing material according to the present invention are used, the deterioration of the thermoelectric conversion material due to the influence of heat at the time of joining is suppressed to a minimum, and the decrease in generated power is suppressed to a minimum. Is done. In addition, melting destruction of the bonding interface when the thermoelectric conversion module is used is prevented. When the melt fracture is prevented, the electrode member and the thermoelectric conversion member are prevented from falling off, and the structure of the thermoelectric conversion module is reliably maintained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a thermoelectric conversion module.
FIG. 2 is a front view showing a thermoelectric conversion member in which iron and nickel are metallized on both end surfaces of the thermoelectric conversion material.
FIG. 3 is a side view showing a joining structure at the time of manufacturing the thermoelectric conversion module.
[Explanation of symbols]
Reference Signs List 10 thermoelectric conversion module 11 thermoelectric conversion member 11a thermoelectric conversion material 12 electrode member 14 brazing material

Claims

A method for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected via an electrode member, wherein the electrode member and a thermoelectric conversion member having the thermoelectric conversion material as a constituent element are brazed. In a method of assembling a thermoelectric conversion module having a joining step,
A method for assembling a thermoelectric conversion module, comprising a step of interposing and joining a silver brazing material having a melting point of 600 ° C. or less between a joining surface of an electrode member and a joining surface of a thermoelectric conversion member.

The method for assembling a thermoelectric conversion module according to claim 1, wherein the brazing material interposed between the joining surfaces is an Ag-Cu-Sn-based or Ag-Cu-In-based brazing material.

The electrode member is made of a pure metal selected from Ni, Cu, Ag, Mo, Pt, Au, Fe, Co, V, W, Nb, Ta, Pd, Ir, Zn, In, Cr, and Al or any of these. The method for assembling a thermoelectric conversion module according to claim 1 or 2, wherein the method is made of an alloy comprising two or more kinds of metals.

The thermoelectric conversion member has Ni, Cu, Ag, Mo, Pt, Au, Fe, Co, V, W, Nb, Ta, Pd, Ir, Zn, In, Cr, The assembly of the thermoelectric conversion module according to any one of claims 1 to 3, wherein a pure metal selected from Al or an alloy including two or more of these metals has a metallized layer. Method.

A brazing material for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected via an electrode member,
A brazing material for assembling thermoelectric conversion modules having a melting point of 600 ° C. or less and a Vickers hardness (HV) at 400 ° C. to 500 ° C. of the alloy obtained after melting of 100 to 200.

The brazing material used for assembling the thermoelectric conversion module according to claim 5, which is an Ag-Cu-Sn-based or Ag-Cu-In-based.

A thermoelectric conversion module assembled by the method for assembling a thermoelectric conversion module according to claim 1.

The thermoelectric conversion module according to claim 7, further comprising an alloy layer containing Ag, Cu, and Sn as main components or an alloy layer containing Ag, Cu, and In as main components at a bonding interface between the thermoelectric conversion member and the electrode member.