JP2004186566A

JP2004186566A - Assembling method of thermoelectric conversion module

Info

Publication number: JP2004186566A
Application number: JP2002353931A
Authority: JP
Inventors: Kenichi Miyazaki; 兼一宮崎; Tomohiro Shimada; 知宏島田; Hiroyuki Kusamori; 裕之草森
Original assignee: Tanaka Kikinzoku Kogyo KK
Current assignee: Tanaka Kikinzoku Kogyo KK
Priority date: 2002-12-05
Filing date: 2002-12-05
Publication date: 2004-07-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide an assembling method of a thermoelectric conversion module using a bonding step in which a semiconductor may be bonded in a low temperature not to deteriorate a semiconductor device (thermoelectric conversion material) and a fusing point of a bonded portion resulting from bonding becomes a temperature in a high temperature zone. <P>SOLUTION: In the assembling method of the thermoelectric conversion module having the step of using wax 13 to bond an electrode member 12 to a semiconductor chip 11, low fusing point Au-Sn wax 13 is interposed between the bonding surface of the electrode member 12 and the bonding surface of the semiconductor chip 11 and in such a state, a bonding position where the wax 13 is interposed is heated to a temperature higher than a solidus temperature of the wax 13 for 150°C to 430°C to incur liquidus diffusion between the wax 13 and the electrode member 12, thereby bonding the electrode member 12 and the semiconductor chip 11. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、発電等に用いられる熱電変換デバイス等の電子デバイスの組立て方法に関し、特に熱電変換モジュールの組立方法に関する。
【従来の技術】
【０００２】
熱電変換モジュールなどの電子デバイスの組立てでは、部品どうしの接合にろう付けが広く用いられている。ろう付けは、例えば接合対象部材間にろう材を介在させた後に当該ろう材を加熱、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】
例えば、熱電変換モジュール１０（図１および図２参照）は、熱エネルギーを直接電気エネルギー変換するものであり、ｐ型，ｎ型の２種類の半導体チップ（熱電変換材料）１１を有している（図中の符号「ｐ」，「ｎ」は便宜的に付した符号）。これらの半導体チップ１１は電極部材１２を介して交互に接続されており、電気的には直列に接続されている。そして、この半導体チップ１１と電極部材１２との接合においてろう付けが用いられている。
【０００４】
熱電変換モジュールでは、半導体の一方の基板側を比較的高い温度（例えば４００℃〜６００℃）にすると共に他方の基板側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（ゼーベック効果）。また直列に配列された半導体に電流を流すと、いずれか一方の基板側の半導体端部では熱を吸収し、他方の半導体端部側では熱を発生する（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。したがって、熱電変換モジュールにおいては、ろう付けした接合部が使用中に溶融することを防止する必要がある。このようなことから、変換材料と電極部材とのろう付けには、従来、Ａｇ系ろう材（固相線が約６５０℃〜８５０℃）など、高融点の硬ろうが用いられている（特許文献１、特許文献２参照）。
【０００５】
【特許文献１】
特開２０００−１５６５２９号公報
【特許文献２】
特開平５−５５６３８号公報
【０００６】
【発明が解決しようとする課題】
ところが、Ａｇ系ろう材などの硬ろうを用いると、高い温度でろう付けしなければならず、接合時の熱で半導体素子を劣化させてしまうことがある。半導体素子が劣化するとエネルギー変換効率が低下してしまうといった不具合が生ずる。このようなことから、実際の電子部品の組立てでは、ろう材の選択肢として、ろう付け温度がより低いろう材、例えば中低温領域（４００℃〜６５０℃）のろう材が望まれている。ただし、前述したように、熱電変換モジュールは使用中に高温になる部分を有していることから、ろう付けによって得られる接合部の融点（再溶融温度）はできるだけ高温（例えば６５０℃以上）であるのが望ましい。
【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、半導体素子を劣化させることのない中低温領域またはそれ以下の温度領域の温度でろう付けでき、かつろう付け後に得られる接合部の融点が高温域の温度になる接合工程を用いた熱電変換モジュールの組立方法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】
上記課題を解決するため、発明者らは、低融点のろう材を用いて接合を行う場合の加熱温度条件について検討した。その結果、通常のろう付け温度を上回る高温域の温度に加熱して接合すると、ろう材が溶融した後に接合対象物との間で液相での相互拡散が生じて、接合対象物相互の接合部（接合界面）が合金化し、接合時の加熱温度より高温の融点（再溶融温度）を有する接合部が得られる場合があることを見出し、本発明に想到するに至った。
【０００９】
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直列接続されてなる熱電変換モジュールの組立方法であり、電極部材をろう材を用いて接合対象物に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、前記電極部材の接合面と前記接合対象物の接合面との間に低融点のろう材を介在させ、この状態でろう材が介在される接合位置をろう材の固相線温度より１５０℃〜５３０℃高い温度に加熱してろう材と電極部材との間で液相拡散を生じさせて電極部材と接合対象物とを接合する工程を有することを特徴とする。
【００１０】
熱電変換モジュールの組立てでは、電極部材を、熱電変換材料やリード線の端子などの部材（接合対象物）と接合する工程がある。例えば、電極部材と熱電変換材料とを接合する場合は、まず両部材の接合面間に低融点のろう材（固相線温度が約１２０℃〜４５０℃のろう材）を介在させる。低融点のろう材としては、Ａｕ−Ｓｎ２０ろう材（Ａｕ：８０重量％、Ｓｎ：２０重量％）等のＡｕ系ろう材などがある。
【００１１】
Ａｕ−Ｓｎろう材には、固相線が比較的低温（２１７℃〜２７８℃）のものがあり、通常のろう付けでは２２０℃〜３３０℃に加熱されて用いられる。このろう材を、本発明では、通常より１５０℃〜４３０℃も高い３７０℃〜６５０℃に加熱して接合を行う。
【００１２】
このような加熱温度で接合を行うと、ろう材と電極部材との間において、通常のろう付けでは生じにくい液相相互拡散が促進される。そして、ろう材だけでなく電極部材の一部をも含む部分が合金化する。例えば、電極部材がＮｉ製であり、ろう材がＡｕ−Ｓｎろう材であれば、Ｎｉを含む電極部材とろう材との間で相互拡散が生じて、接合部にＡｕ，Ｎｉ，Ｓｎからなる再溶融温度（固相線温度）が高い温度（具体的には約７００℃以上）の合金が生成される。つまり、上述したような接合工程を用いれば、６５０℃以下という中低温領域の接合温度で、中低温領域よりも高い６５０℃以上の再溶融温度を有する接合部が得られる。
【００１３】
このように、本発明で用いられる接合工程は、接合温度が低温であって、かつ６５０℃以上という高温の再溶融温度を有する接合部が得られるという特徴を有する。したがって、熱電変換モジュールで用いられる電極部材を熱電変換材料などの他の部材と接合する際に用いる方法として好適である。そして、特に電極部材と熱電変換材料とを接合する工程として好適である。接合温度が上述したような中低温領域（例えば３７０℃〜６５０℃）であれば、接合時の加熱による熱電変換材料の劣化を防止できるからである。熱電変換モジュールはモジュール全体に多数の熱電変換材料を備えており、電極部材の接合対象が熱電変換材料である場合はもちろん、熱電変換材料でない場合であっても加熱位置に隣接して熱電変換材料が存在する場合が考えられる。このような場合に接合温度が高ければ、熱電変換材料を劣化するおそれがある。また、再溶融温度が高温であれば、使用時における熱電変換モジュールの溶融破壊を防止できるという利点が得られる。先に説明したように、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が、６５０℃以上という高温の再溶融温度を有する接合部が得られれば、モジュール使用中の接合部の溶融破壊が防止される。
【００１４】
また、上記の内容から解るように、この接合工程によれば、電極部材と他方の接合対象物との接合箇所にＡｕ−Ｓｎろう材などの低融点ろう材だけを介在させて加熱するだけで、６５０℃以上といった高温の再溶融温度を有する接合部を得て両部材を接合できる。ろう付けなど、接合箇所にろう材を介在させて加熱する接合工程では、接合箇所に介在させる物の数が多くなると、その分、セッティングに時間を要することとなるが、本発明によれば、介在させるものを最小限に抑えることができ、迅速、容易かつ確実に接合作業を行うことができる。
【００１５】
このように作業性の面で優れる接合方法を実現できる理由、つまり介在物の数が最小限に抑えられる理由の一つとして、熱電変換モジュールの電極部材に、ＡｕやＳｎ等のろう材成分金属と合金化して高い再溶融温度（固相線温度）を有する合金を構成し得るＮｉ等の成分が豊富に含まれている、ということがある。そして、もう一つの理由として、接合時の加熱温度条件が通常のろう付け温度を大きく上回る高温域の温度である、ということがある。このように高温域の温度に加熱すると、ろう材と電極部材との間で物質の液相相互拡散が生じ、電極部材中に豊富に存在するＮｉ等の合金生成に欠かせない成分が利用され、高い再溶融温度を有する合金が接合部に迅速かつ確実に生成される。
【００１６】
上記の接合工程で、接合面間に介在させて用いる低融点のろう材としては、検討の結果、Ａｕ，Ｓｎ，Ｇｅ，Ｓｉ，Ｉｎ，Ａｇ，Ｃｕから選択される１種または２種以上の金属からなるろう材であって、固相線の温度が５００℃以下のろう材を挙げることができるということが解った。そして、この中でも、Ａｕ−Ｓｎ系、Ａｕ−Ｇｅ系、Ａｕ−Ｓｉ系、Ａｕ−Ｉｎ系、Ｓｎ−Ｉｎ系、Ｓｎ−Ａｇ系のろう材のろう材が好ましいことが解った。
【００１７】
例えばＡｕ−Ｓｎ系のろう材の場合、固相線の温度が２１７℃〜４００℃であるろう材、別言すればＡｕ−Ｓｎ１０〜９０ろう材（Ａｕ：１０〜９０重量％、Ｓｎ：１０〜９０重量％のろう材）が好ましく、特にＳｎの含有量が１９〜２１重量％の範囲にあるＡｕ−Ｓｎ２０ろう材（Ａｕ：８０重量％、Ｓｎ：２０重量％のろう材）が好ましい。このように、ろう材の組成を特定することで、本発明で用いるろう材として好ましい低融点のろう材を特定できる。そこで、Ａｕ−Ｓｎ以外の各ろう材について、その組成に基づき、好ましいろう材を説明する。
Ａｕ−Ｇｅ系のろう材の場合、Ａｕ−Ｇｅ５〜２５ろう材（Ａｕ：７５〜９５重量％、Ｇｅ：５〜２５重量％のろう材）が好ましく、特にＧｅの含有量が１２〜１３重量％の範囲にあるＡｕ−Ｇｅ１２．５ろう材（Ａｕ：８７．５重量％、Ｇｅ：１２．５重量％のろう材（固相線は３６１℃））が好ましい。
Ａｕ−Ｓｉ系のろう材の場合、Ａｕ−Ｓｉ１〜１０ろう材（Ａｕ：９０〜９９重量％、Ｓｉ：１〜１０重量％のろう材）、特にＳｉの含有量が２．５〜４重量％の範囲にあるＡｕ−Ｓｉ３．１５ろう材（Ａｕ：９６．８５重量％、Ｓｉ：３．１５重量％のろう材（固相線は３６３℃））が好ましい。
Ａｕ−Ｉｎ系のろう材の場合は、Ａｕ／１４〜８６Ｉｎろう材（Ａｕ：１４〜８６重量％、Ｉｎ：１４〜８６重量％のろう材（固相線は１５６℃〜５４１℃））が好ましく、特にＩｎの含有量が１４〜５４重量％の範囲にあるＡｕ−Ｉｎ２７ろう材（Ａｕ：７３重量％、Ｉｎ：２７重量％のろう材（固相線は４５８℃））が好ましい。
Ｓｎ−Ｉｎ系のろう材の場合は、Ｓｎ−０〜１００Ｉｎろう材（Ｓｎ：０〜１００重量％、Ｉｎ：０〜１００重量％のろう材（固相線は１２０℃〜２３２℃））が好ましく、特にＩｎの含有量が４５〜７５重量％の範囲にあるＳｎ−Ｉｎ５１ろう材（Ｓｎ：４９重量％、Ｉｎ：５１重量％のろう材（固相線は１２０℃））が好ましい。
Ｓｎ−Ａｇ系のろう材の場合は、Ｓｎ−２．５〜５０Ａｇろう材（Ｓｎ：５０〜９７．５重量％、Ａｇ：２．５〜５０重量％のろう材（固相線は２２１℃）が好ましい。
なお、本発明に係るモジュールの組立て方法で用いられる接合方法は拡散を生じさせて接合するというものであることから、接合時の加熱温度は、いずれのろう材の場合であっても、５００℃〜６５０℃の温度であってしかも実際に接合に用いられるろう材の固相線温度よりも１５０℃以上高い温度が好ましい。
【００１８】
これらのろう材を用い、上記中低温領域の温度条件で加熱して接合を行うと、Ａｕ−Ｓｎ２０ろう材を用いた場合と同様、ろう材と電極などの接合対象との間で相互拡散が適度に生じて接合部が合金化し、中低温領域よりも高温（６５０℃以上）の再溶融温度（固相線温度）を有する接合部が得られる。融点が中低温領域よりも高温である接合部が得られれば、上述したように、熱電変換モジュール使用中に接合部が溶融によって破壊されるようなことを防止できる。
【００１９】
また、接合部が合金化して融点が上昇する点について、先に挙げた種々のろう材を用いてさらに検討した。その結果、接合時にろう材との間で相互拡散する金属の種類によっては、接合後、比較的酸化しやすい合金が生ずる場合があるなど、耐久性の面でバラツキがあることが解った。そこで、より耐久性に優れるなど、より優れた接合品質の接合部が得られるろう付け方法について検討した。その結果、電極部材としては、Ａｌ、Ｃｒ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｎｂ、Ｍｏ、Ｉｎ、Ｔａ、Ｗ、Ｉｒ、Ｐｔ、Ａｕ、Ｐｄ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好ましいことが解った。２種以上の金属としては、ＣｕＮｉ、ＣｕＷ、ＦｅＮｉ、コバール（ＫＯＶＡＲ（登録商標））などのＦｅＮｉＣｏ合金あるいはＳＵＳ３０４などのステンレス（ＦｅＣｒＮｉ合金）などを挙げることができる。そして、これらの中でも電極部材としては、Ｎｉ、Ｃｕ、ＣｕＮｉ、ＣｕＷ、ＦｅＮｉ、コバール、ＳＵＳ３０４などのステンレスがより好ましい。電極部材がこれらの素材からなるものまたはこれらの素材で被覆されたものであれば、ろう材と電極部材との間における適度な相互拡散の結果生ずる合金は酸化しにくく、耐久性に優れるなど、優れた特性を有しているからである。
【００２０】
ただし、熱電変換材料側の接合界面においては十分な接合強度を得ることができない場合がある。そこで、この点について検討した結果、熱電変換材料の接合界面にＮｉ等の金属があれば十分な接合強度が得られることが解った。Ｎｉ等の金属を存置させることで、熱電変換材料の接合面のぬれ性が向上するからであると考えられる。Ｎｉ等の金属を存置させる方法としては、熱電変換材料の接合界面にＮｉなどの金属をメタライズする方法が好ましい。メタライズしておけば、電極部材と熱電変換材料との間にろう材を介在させるだけでよく、接合時の作業性が損なわれないという利点がある。熱電変換材料の接合界面にメタライズする材料としては、Ａｌ、Ｃｒ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｎｂ、Ｍｏ、Ｉｎ、Ｔａ、Ｗ、Ｉｒ、Ｐｔ、Ａｕ、Ｐｄ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ものが好ましい。２種以上の金属としては、ＣｕＮｉ、ＣｕＷ、ＦｅＮｉ、コバールなどのＦｅＮｉＣｏ合金あるいはＳＵＳ３０４などのＦｅＣｒＮｉ合金などを挙げることができる。そして、これらの中でも電極部材としては、Ｎｉ、Ｃｕ、ＣｕＮｉ、ＣｕＷ、ＦｅＮｉ、コバール、ＳＵＳ３０４などのステンレスがより好ましい。メタライズ方法としては、ホットプレス法（ＨＰ法）、プリント法、めっき、溶射またはプラズマ放電焼結法（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。
【００２１】
ここで、熱電変換材料の接合面にメタライズする金属量について検討した。例えば、Ｎｉ製の電極部材と熱電変換材料とをＡｕ−Ｓｎ２０ろう材を用いて接合する場合であれば、接合部に得られる合金はＡｕ，Ｎｉ，Ｓｎからなるものであり、熱電変換材料の接合面にメタライズする好適な金属としてＮｉが考えられる。この場合に、介在させたろう材の全てが拡散に寄与する状態（換言すれば、介在させたろう材の全てが合金化する状態）を得るには、ろう材「８」に対してＮｉが「２」以上の割合で必要になる（重量比基準）が、検討の結果、本発明では、熱電変換材料の接合面にメタライズするＮｉの比率（重量比）は、ろう材「８」に対して「１」あれば良いことが解った。もちろん「１」以上の比率になる量のＮｉをメタライズしても良い。また、Ｃｕ製の電極部材と熱電変換材料をＡｕ−Ｓｎ２０ろう材を用いて接合する場合についても同様に検討した。この場合、接合部に得られる合金はＡｕ，Ｃｕ，Ｓｎからなるものであり、熱電変換材料の接合面にメタライズする金属としてはＣｕが好ましい。そして、介在させたろう材の全てが拡散に寄与する状態を得るには熱電変換材料の接合面にメタライズするＣｕの比率（重量比）は、ろう材「７」に対して「３」であるが、検討の結果、熱電変換材料の接合面にメタライズするＣｕの比率（重量比）は、ろう材「７」に対して「１．５」あれば良いことが解った。もちろん「１．５」以上の比率になる量のＣｕをメタライズしても良い。本発明では、電極部材とろう材との間での相互拡散を生じさせることで、電極部材に含まれるＮｉやＣｕなどの合金化に必要な金属を利用できるからであると考えられる。
【００２２】
また、本発明で行われる接合工程で用いることができる好適なろう材として先に列挙したろう材は、ろう付け温度が中低温領域であり、また拡散ろう付けによって得られる接合部の融点はろう付け温度以上（例えば６５０℃以上）である。これらの理由から、これらのろう材は、ステップろう付けにおける中低温領域用ステップの代替工程として好適であることを見出した。
【００２３】
例えば、まず最初に、固相線温度が約２８０℃であるＡｕ−Ｓｎ２０ろう材を用いて、電極部材と熱電変換材料とを接合すると、先に説明したように、固相線温度（再溶融温度）が６５０℃以上の接合部が得られる。このように再溶融温度が高温である接合部を得られる点は、Ａｕ−Ｇｅ系ろう材、Ａｕ−Ｓｉ系ろう材（固相線温度は約３６０℃）あるいはＡｕ−Ｉｎ系、Ｓｎ−Ｉｎ系、Ｓｎ−Ａｇ系のろう材など、他のろう材を用いた場合も同様である。したがって、接合終了後、最初に用いたろう材と同じ材質のろう材を用いて、最初の接合で得られた接合部を溶融させることなく、例えば電極部材等にさらに別の部材をろう付けできる。
【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の好適な実施形態を説明する。
【００２５】
第１実施形態：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、ｎ型，ｐ型の半導体チップ（熱電変換材料）１１を電極部材１２で挟んだ構造である。２種類の半導体チップ１１は、電極部材１２を介して交互に接続されており、電気的に直列に接続されている。そして、半導体チップ１１を接続する電極部材１２が半導体チップ１１の上下に交互に位置するように、半導体チップ１１および電極部材１２の配置が定められている。なお、この実施形態で用いた半導体チップ１１はＮａＣｏ_２Ｏ_４系の半導体であり、電極部材はＮｉ製であった。
【００２６】
以下、本実施形態の熱電変換モジュールの組立てについて説明する。
【００２７】
まず、用意したＮｉ製の板材を切断して、長方形（６ｍｍ×１４ｍｍ×２ｍｍ）の板材を得た。これは熱電変換モジュールの電極部材１２として用いられるものである。次に、ｎ型，ｐ型のそれぞれについて用意した半導体材料について、まずホットプレスによって成形・焼結して５０ｍｍ×５０ｍｍ×８ｍｍに切断した。その後、電極部材１２との接合面（最も広い上下の端面）に溶射によって２ｍｍ厚のＮｉ層１１ａを形成（メタライズ）し（図２参照）、形成したＮｉ層１１ａの外表面を平滑に研摩した。そして、６ｍｍ×６ｍｍ×８ｍｍに切断して、他方の接合対象物となる半導体チップ１１を得た。
【００２８】
また、半導体チップ１１と電極部材１２との接合に用いるＡｕ−Ｓｎ２０ろう材１３（図２参照）を製造した。まず、溶解鋳造によって、Ａｕが８０重量％でＳｎが２０重量％のインゴットを製造し、このインゴットに押出加工および圧延加工を施して箔状（２０μｍ厚）のＡｕ−Ｓｎ２０ろう材を得た。これを所定の大きさに切断して接合に用いるろう材１３を得た。
【００２９】
この後、半導体チップ１１と電極部材１２を接合した。まず、図２に示されるように、接合端面が上下に位置するように交互に配置されたｎ型，ｐ型の半導体チップ１１の上下に、Ａｕ−Ｓｎ２０ろう材１３を介在させた状態でＮｉ製の電極部材１２を、カーボン製の治具（不図示）を用いて配置した。そして、ろう材１３が介在された接合部を加熱して半導体チップ１１と電極部材１２を接合し、熱電変換モジュール１０を得た。接合時の条件は、加熱温度が６００℃、加熱時間が１０分間、水素含有窒素ガス（Ｎ_２−３容積％Ｈ_２ガス）雰囲気中で行うというものであった。なお、得られた熱電変換モジュール１０は、例えば通電用のリード線１４の端子１４ａをろう付け（図１参照）あるいはねじ止めされるなどして用いられる。
【００３０】
第２〜第６実施形態：接合工程で用いるＡｕ−Ｓｎろう材の組成比、電極部材の材質、および半導体チップに溶射（メタライズ）する金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は第１実施形態と同じであったので、その説明を省略する。各実施形態におけるそれぞれの条件は表１に示す通りである。
【００３１】
比較例１：接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第１実施形態と同じであった。条件は表１に示す通りである。
【００３２】
接合部の評価：各実施形態および比較例で得られた熱電変換モジュールの半導体チップ１１と電極部材１２との接合部をサンプリングし、常温から７００℃の温度範囲で、示差熱・熱重量同時測定（ＴＧ／ＤＴＡ）を行って、溶融に伴うピーク（吸熱ピーク）がＤＴＡ曲線上に有るか否かを調べた。また、図３に示されるような半導体チップ１１の両端に電極部材１２を接合した試験片を作り、各電極部材１２をそれぞれペンチで挟んで、両電極部材１２を半導体チップ１１から引き剥がすように矢印Ｂの方向に引っ張って接合強度を測定した。そして、半導体チップ（素子）１１の部分で破壊したものを「良好」と評価し、ろう材による接合部で破壊したものを「不良」と評価した。これらの測定結果を表１に示す。なお、以下に説明する各実施形態および比較例で得られた熱電変換モジュールの接合部についても、同様の方法で再溶融温度および接合強度を測定した。
【００３３】
【表１】

【００３４】
表１に示されるように、各実施形態では、接合時の加熱温度をろう材の固相線温度（２７８℃）よりも約３３０℃高い温度にした結果、６５０℃以上という高い融点（再溶融温度）の接合部を得ることができた。したがって、熱電変換モジュール使用時にモジュールが高温になっても、接合部が溶融してモジュールが破壊するようなことを防止できることが解った。また、接合強度も十分に高く良好であった。一方、従来のろう付けで用いられている温度に加熱した比較例１では、高温の再溶融温度を有する接合部を得ることができず、高温時に接合部が溶融するおそれがあることが解った。この結果、実施形態の組立て方法を用いれば、高い再溶融温度を有し、かつ高い接合強度を有する接合部が得られることが解った。
【００３５】
第７〜第９実施形態：第１実施形態とは異なるろう材を用いて熱電変換モジュールを製造した。用いたろう材はＡｕ−Ｇｅろう材であった。また、第７〜第９実施形態ごとに、用いるＡｕ−Ｇｅろう材の組成比、電極部材の材質、および半導体チップにメタライズする金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は第１実施形態と同じであった。各実施形態におけるそれぞれの条件は表２に示す通りである。
【００３６】
比較例２：表２に示されるように、接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第７実施形態と同じであった。
【００３７】
【表２】

【００３８】
第１０〜１２実施形態：第１実施形態とは異なるろう材を用いて熱電変換モジュールを製造した。用いたろう材はＡｕ−Ｓｉろう材であった。また、第１０〜第１２実施形態ごとに、用いるＡｕ−Ｓｉろう材の組成比、電極部材の材質、および半導体チップにメタライズする金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は第１実施形態と同じであった。各実施形態におけるそれぞれの条件は表３に示す通りである。
【００３９】
比較例３：表３に示されるように、接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第１０実施形態と同じであった。
【００４０】
【表３】

【００４１】
第１３〜１５実施形態：第１実施形態とは異なるろう材を用いて熱電変換モジュールを製造した。用いたろう材はＡｕ−Ｉｎろう材であった。また、第１３〜第１５実施形態ごとに、用いるＡｕ−Ｉｎろう材の組成比、電極部材の材質、および半導体チップにメタライズする金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は、加熱温度に多少の違いが生じたものの、第１実施形態と同じであった。各実施形態におけるそれぞれの条件は表４に示す通りである。
【００４２】
比較例４：表４に示されるように、接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第１３実施形態と同じであった。
【００４３】
【表４】

【００４４】
第１６〜１８実施形態：第１実施形態とは異なるろう材を用いて熱電変換モジュールを製造した。用いたろう材はＳｎ−Ｉｎろう材であった。また、第１６〜第１８実施形態ごとに、用いるＳｎ−Ｉｎろう材の組成比、電極部材の材質、および半導体チップにメタライズする金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は第１実施形態と同じであった。各実施形態におけるそれぞれの条件は表５に示す通りである。
【００４５】
比較例５：表５に示されるように、接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第１６実施形態と同じであった。
【００４６】
【表５】

【００４７】
第１９〜２１実施形態：第１実施形態とは異なるろう材を用いて熱電変換モジュールを製造した。用いたろう材はＳｎ−Ａｇろう材であった。また、第１９〜第２１実施形態ごとに、用いるＳｎ−Ａｇろう材の組成比、電極部材の材質、および半導体チップにメタライズする金属に関する条件を必要に応じて変えて、熱電変換モジュールを製造した。これら以外の条件は第１実施形態と同じであった。各実施形態におけるそれぞれの条件は表６に示す通りである。
【００４８】
比較例６：表６に示されるように、接合時の加熱温度条件を変えて熱電変換モジュールを製造した。これ以外の条件は第１９実施形態と同じであった。
【００４９】
【表６】

【００５０】
表２から表６に示されるように、Ａｕ−Ｓｎろう材以外のろう材を用いた場合にもＡｕ−Ｓｎろう材と同様の結果が得られた。つまり、６５０℃以上あるいは７００℃以上という高い融点（再溶融温度）の接合部を得ることができた。したがって、高温になる熱電変換モジュール使用時に、接合部が溶融してモジュールが破壊するようなことを防止できることが解った。また、接合強度自体も十分に高いことが解った。一方、従来のろう付け方法を用いた各比較例では、高温の再溶温度を有する接合部を得ることができなかった。そして、接合強度が十分でない場合があった。この結果、Ａｕ−Ｓｎろう材以外のろう材についても、各実施形態の組立て方法を用いれば、半導体チップと電極部材との接合部として、高い再溶融温度を有し、高い接合強度を有する接合部が得られることが解った。
【００５１】
【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を用いれば、電極部材を例えば熱電変換材料と接合する際、低融点ろう材を用い、中低温領域の接合温度で加熱することによって、高温の再溶融温度を有する接合部を得ることができる。接合温度を低く抑えることができれば、接合時の熱電変換材料などの接合対象物の劣化が防止される。また、接合部の再溶融温度が高温であれば、熱電変換モジュール使用時に接合部が溶解するようなことが防止され、熱電変換モジュールの耐久性や信頼性が向上する。
【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】熱電変換モジュールの接合構造を示す、図１の矢印Ａ方向の側面図。
【図３】接合強度の試験片を示す側面図。
【符号の説明】
１０熱電変換モジュール
１１半導体チップ（熱電変換材料、他の接合対象物）
１１ａＮｉ層（メタライズにより形成された金属層）
１２電極部材
１３ろう材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for assembling an electronic device such as a thermoelectric conversion device used for power generation or the like, and particularly to a method for assembling a thermoelectric conversion module.
[Prior art]
[0002]
In the assembly of electronic devices such as thermoelectric conversion modules, brazing is widely used for joining parts together. Brazing is, for example, a joining method in which a brazing material is interposed between members to be joined and then heated and melted to join the two 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]
For example, the thermoelectric conversion module 10 (see FIGS. 1 and 2) directly converts heat energy into electric energy, and has two types of semiconductor chips (thermoelectric conversion materials) 11 of p-type and n-type. (The symbols “p” and “n” in the figure are symbols attached for convenience). These semiconductor chips 11 are alternately connected via electrode members 12 and are electrically connected in series. Brazing is used in joining the semiconductor chip 11 and the electrode member 12.
[0004]
In a thermoelectric conversion module, when one substrate side of a semiconductor is set to a relatively high temperature (for example, 400 ° C. to 600 ° C.) and the other substrate side is set to a relatively low temperature, a thermoelectromotive force corresponding to the temperature difference is generated. (Seebeck effect). When a current is applied to the semiconductors arranged in series, heat is absorbed at one of the semiconductor ends on the substrate side, and heat is generated at the other semiconductor end (Peltier effect). Thus, the thermoelectric conversion module has a portion that becomes relatively hot during use. Therefore, in the thermoelectric conversion module, it is necessary to prevent the brazed joint from melting during use. For this reason, a high melting point hard solder such as an Ag-based brazing material (having a solidus of about 650 ° C. to 850 ° C.) is conventionally used for brazing the conversion material and the electrode member (Patent) Reference 1, Patent Document 2).
[0005]
[Patent Document 1]
JP 2000-156529 A
[Patent Document 2]
JP-A-5-55638
[0006]
[Problems to be solved by the invention]
However, if a hard brazing material such as an Ag-based brazing material is used, the brazing must be performed at a high temperature, and the heat at the time of joining may deteriorate the semiconductor element. Deterioration of a semiconductor element causes a problem that energy conversion efficiency is reduced. For this reason, in actual assembly of electronic components, as a brazing material option, a brazing material having a lower brazing temperature, for example, a brazing material in a medium to low temperature range (400 ° C. to 650 ° C.) is desired. However, as described above, since the thermoelectric conversion module has a portion that becomes hot during use, the melting point (remelting temperature) of the joint obtained by brazing is as high as possible (for example, 650 ° C. or more). It is desirable to have.
[0007]
The present invention has been made in view of the above background, and can be brazed at a temperature in a low-temperature region or a lower temperature region without deteriorating a semiconductor element, and a bonding portion obtained after brazing. It is an object of the present invention to provide a method for assembling a thermoelectric conversion module using a bonding step in which the melting point of the thermoelectric conversion module becomes a high-temperature range.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the inventors have studied heating temperature conditions when joining is performed using a brazing material having a low melting point. As a result, when joining by heating to a high temperature range higher than the normal brazing temperature, after the brazing material is melted, mutual diffusion occurs in the liquid phase with the joining object, and the joining objects are joined. It has been found that a joint (joining interface) is alloyed, and a joint having a melting point (remelting temperature) higher than the heating temperature during joining may be obtained, and the present invention has been reached.
[0009]
The present invention is a method for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected in series via an electrode member, and includes a step of joining the electrode member to an object to be joined using a brazing material. In the method for assembling a conversion module, a low-melting-point brazing material is interposed between the joining surface of the electrode member and the joining surface of the object to be joined, and in this state, the joining position where the brazing material is interposed is fixed to the brazing material. The method is characterized in that the method includes a step of heating to a temperature higher than the phase line temperature by 150 ° C. to 530 ° C. to cause liquid phase diffusion between the brazing material and the electrode member to join the electrode member and the object to be joined.
[0010]
In assembling a thermoelectric conversion module, there is a step of joining an electrode member to a member (object to be joined) such as a thermoelectric conversion material or a terminal of a lead wire. For example, when joining the electrode member and the thermoelectric conversion material, first, a low melting point brazing material (a brazing material having a solidus temperature of about 120 ° C. to 450 ° C.) is interposed between the joining surfaces of both members. Examples of the low melting point brazing material include Au-based brazing materials such as Au-Sn20 brazing material (Au: 80% by weight, Sn: 20% by weight).
[0011]
Some Au-Sn brazing materials have a relatively low solidus temperature (217 ° C. to 278 ° C.), and are heated to 220 ° C. to 330 ° C. in normal brazing. In the present invention, the brazing material is heated to 370 ° C. to 650 ° C. which is higher than usual by 150 ° C. to 430 ° C. to perform joining.
[0012]
When joining is performed at such a heating temperature, liquid-phase mutual diffusion, which is unlikely to occur with normal brazing, is promoted between the brazing material and the electrode member. Then, not only the brazing material but also a part including a part of the electrode member is alloyed. For example, if the electrode member is made of Ni and the brazing material is an Au-Sn brazing material, mutual diffusion occurs between the electrode member containing Ni and the brazing material, and the joining portion is made of Au, Ni, and Sn. An alloy having a high remelting temperature (solidus temperature) (specifically, about 700 ° C. or higher) is generated. That is, by using the above-described bonding process, a bonding portion having a re-melting temperature of 650 ° C. or higher, which is higher than that of the medium-low temperature region, can be obtained at a bonding temperature of the low-temperature region of 650 ° C. or less.
[0013]
As described above, the bonding step used in the present invention is characterized in that a bonding portion having a low re-melting temperature of 650 ° C. or higher can be obtained at a low bonding temperature. Therefore, it is suitable as a method used when joining the electrode member used in the thermoelectric conversion module to another member such as a thermoelectric conversion material. And it is suitable especially as a process of joining an electrode member and a thermoelectric conversion material. This is because if the joining temperature is in the above-mentioned medium / low temperature range (for example, 370 ° C. to 650 ° C.), deterioration of the thermoelectric conversion material due to heating during joining can be prevented. The thermoelectric conversion module is provided with a large number of thermoelectric conversion materials throughout the module.The thermoelectric conversion material is adjacent to the heating position even when the bonding target of the electrode member is a thermoelectric conversion material or even if it is not a thermoelectric conversion material. May exist. In such a case, if the bonding temperature is high, the thermoelectric conversion material may be deteriorated. Further, when the remelting temperature is high, there is obtained an advantage that the melt breakage of the thermoelectric conversion module during use can be prevented. As described above, the thermoelectric conversion module has a portion that becomes relatively hot during use. However, if a joint having a high re-melting temperature of 650 ° C. or more can be obtained, the melting of the joint during use of the module is possible. Destruction is prevented.
[0014]
Further, as can be understood from the above description, according to this bonding step, only a low-melting-point brazing material such as an Au-Sn brazing material is interposed and heated at a joint between the electrode member and the other joining object. And a member having a high re-melting temperature such as 650 ° C. or more can be joined. In the joining step of heating with a brazing material interposed at the joint, such as brazing, if the number of objects to be interposed at the joint is increased, it takes time for setting, but according to the present invention, Objects can be minimized, and the joining operation can be performed quickly, easily and reliably.
[0015]
One of the reasons why the bonding method excellent in workability can be realized, that is, the reason why the number of inclusions can be minimized is that the electrode member of the thermoelectric conversion module is made of an alloy with a brazing metal such as Au or Sn. In some cases, Ni or the like is abundantly contained which can be converted into an alloy having a high remelting temperature (solidus temperature). Another reason is that the heating temperature condition at the time of joining is a temperature in a high temperature range that is much higher than a normal brazing temperature. When heated to a high temperature range in this way, liquid-phase interdiffusion of a substance occurs between the brazing material and the electrode member, and components abundant in the electrode member, such as Ni, which are indispensable for forming an alloy, are used. An alloy having a high remelting temperature is quickly and reliably produced at the joint.
[0016]
As a result of the examination, as a low melting point brazing material used to be interposed between the joining surfaces in the above joining step, one or two or more kinds selected from Au, Sn, Ge, Si, In, Ag, and Cu are examined. It has been found that a brazing material made of metal and having a solidus temperature of 500 ° C. or less can be given. And among these, it turned out that the brazing material of Au-Sn system, Au-Ge system, Au-Si system, Au-In system, Sn-In system, and Sn-Ag system brazing material is preferable.
[0017]
For example, in the case of an Au—Sn brazing material, a brazing material having a solidus temperature of 217 ° C. to 400 ° C., in other words, an Au—Sn 10 to 90 brazing material (Au: 10 to 90% by weight, Sn: 10) To 90% by weight), and more preferably an Au-Sn20 brazing material having a Sn content in the range of 19 to 21% by weight (Au: 80% by weight, Sn: 20% by weight). Thus, by specifying the composition of the brazing material, a low-melting-point brazing material that is preferable as the brazing material used in the present invention can be specified. Therefore, for each brazing material other than Au-Sn, preferred brazing materials will be described based on their compositions.
In the case of an Au-Ge brazing material, an Au-Ge brazing material (Au: 75 to 95% by weight, Ge: 5 to 25% by weight) is preferable, and particularly, the content of Ge is 12 to 13% by weight. % (Au: 87.5% by weight, Ge: 12.5% by weight (solidus line: 361 ° C.)).
In the case of an Au-Si-based brazing material, Au-Si 1-10 brazing material (Au: 90-99% by weight, Si: 1-10% by weight), in particular, the content of Si is 2.5-4% by weight. % Of Au—Si 3.15% by weight (Au: 96.85% by weight, Si: 3.15% by weight (solidus temperature is 363 ° C.)).
In the case of an Au-In brazing material, an Au / 14 to 86 In brazing material (Au: 14 to 86 wt%, In: 14 to 86 wt% brazing material (solid line 156 ° C to 541 ° C)) is used. Au-In27 brazing material having an In content in the range of 14 to 54% by weight (Au: 73% by weight, In: 27% by weight (solidus line: 458 ° C.)) is particularly preferable.
In the case of Sn-In-based brazing material, Sn-0 to 100In brazing material (Sn: 0 to 100% by weight, In: 0 to 100% by weight) (solid phase line: 120 ° C to 232 ° C) is used. In particular, a Sn-In51 brazing filler metal having an In content in the range of 45 to 75% by weight (Sn: 49% by weight, In: 51% by weight brazing filler metal (solidus temperature: 120 ° C.)) is preferred.
In the case of Sn-Ag brazing material, Sn-2.5 to 50 Ag brazing material (Sn: 50 to 97.5 wt%, Ag: 2.5 to 50 wt% brazing material (solidus temperature is 221 ° C.) Is preferred.
Since the bonding method used in the method of assembling the module according to the present invention involves bonding by causing diffusion, the heating temperature at the time of bonding is 500 ° C. regardless of the brazing material. It is preferable that the temperature be from about 650 ° C. to 150 ° C. higher than the solidus temperature of the brazing material actually used for joining.
[0018]
When bonding is performed by using these brazing materials and heating under the above-mentioned medium-low temperature range temperature conditions, mutual diffusion between the brazing material and a bonding target such as an electrode is performed similarly to the case of using the Au-Sn20 brazing material. A moderately generated joint is alloyed, and a joint having a re-melting temperature (solidus temperature) higher (650 ° C. or higher) than the medium-low temperature region is obtained. If a joint having a melting point higher than that of the medium / low temperature region is obtained, it is possible to prevent the joint from being broken by melting during use of the thermoelectric conversion module, as described above.
[0019]
Further, the fact that the melting point rises due to alloying of the joints was further studied using the various brazing materials mentioned above. As a result, it was found that depending on the type of metal interdiffused with the brazing material at the time of joining, an alloy that is relatively easily oxidized after joining may be generated, and the durability varies. Then, the brazing method which can obtain the joining part of more excellent joining quality, such as more excellent durability, was examined. As a result, as the electrode member, a pure metal selected from Al, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, In, Ta, W, Ir, Pt, Au, Pd, or any of these. It has been found that an alloy composed of two or more metals is preferable. Examples of the two or more metals include CuNi, CuW, FeNi, an FeNiCo alloy such as Kovar (KOVAR (registered trademark)), and a stainless steel (FeCrNi alloy) such as SUS304. Among these, stainless steel such as Ni, Cu, CuNi, CuW, FeNi, Kovar, and SUS304 is more preferable as the electrode member. If the electrode member is made of these materials or coated with these materials, the alloy resulting from appropriate mutual diffusion between the brazing material and the electrode member is hardly oxidized and has excellent durability, This is because it has excellent characteristics.
[0020]
However, sufficient bonding strength may not be obtained at the bonding interface on the thermoelectric conversion material side. Therefore, as a result of examining this point, it has been found that if a metal such as Ni is present at the bonding interface of the thermoelectric conversion material, a sufficient bonding strength can be obtained. It is considered that the presence of a metal such as Ni improves the wettability of the bonding surface of the thermoelectric conversion material. As a method for allowing a metal such as Ni to remain, a method in which a metal such as Ni is metallized at the bonding interface of the thermoelectric conversion material is preferable. If metallized, it is only necessary to interpose a brazing material between the electrode member and the thermoelectric conversion material, and there is an advantage that workability at the time of joining is not impaired. The material to be metallized at the bonding interface of the thermoelectric conversion material is a pure metal selected from Al, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, In, Ta, W, Ir, Pt, Au, and Pd. Or those in which an alloy composed of two or more of these metals is metallized. Examples of the two or more metals include FeNiCo alloys such as CuNi, CuW, FeNi, and Kovar, and FeCrNi alloys such as SUS304. Among these, stainless steel such as Ni, Cu, CuNi, CuW, FeNi, Kovar, and SUS304 is more preferable as the electrode member. Various metallization methods such as hot pressing (HP), printing, plating, thermal spraying or plasma discharge sintering (SPS), physical vapor deposition (PVD), and chemical vapor deposition (CVD) are available. There is a way.
[0021]
Here, the amount of metal to be metallized on the bonding surface of the thermoelectric conversion material was examined. For example, in the case where the Ni electrode member and the thermoelectric conversion material are joined by using an Au-Sn20 brazing material, the alloy obtained at the joining portion is made of Au, Ni, Sn, and the thermoelectric conversion material is used. Ni is considered as a suitable metal to be metallized on the bonding surface. In this case, in order to obtain a state in which all of the intervening brazing materials contribute to diffusion (in other words, a state in which all of the intervening brazing materials are alloyed), Ni is set to “2” with respect to brazing material “8”. However, according to the present invention, the ratio (weight ratio) of Ni metallized on the bonding surface of the thermoelectric conversion material is higher than that of the brazing material “8” in the present invention. 1 " Of course, the amount of Ni that becomes a ratio of “1” or more may be metallized. Further, the case where the electrode member made of Cu and the thermoelectric conversion material were joined using the Au-Sn20 brazing material was also examined in the same manner. In this case, the alloy obtained at the joint portion is made of Au, Cu, Sn, and Cu is preferable as the metal to be metallized on the joint surface of the thermoelectric conversion material. Then, in order to obtain a state in which all of the intervening brazing material contributes to diffusion, the ratio (weight ratio) of Cu metallized on the bonding surface of the thermoelectric conversion material is “3” with respect to the brazing material “7”. As a result of the study, it was found that the ratio (weight ratio) of Cu metallized on the bonding surface of the thermoelectric conversion material should be "1.5" with respect to the brazing material "7". Of course, Cu may be metallized in an amount that gives a ratio of “1.5” or more. In the present invention, it is considered that by causing the interdiffusion between the electrode member and the brazing material, metals necessary for alloying such as Ni and Cu contained in the electrode member can be used.
[0022]
In addition, the brazing materials listed above as suitable brazing materials that can be used in the joining step performed in the present invention have a brazing temperature in a medium to low temperature range, and a melting point of a joint obtained by diffusion brazing is low. It is higher than the attachment temperature (for example, 650 ° C. or higher). For these reasons, it has been found that these brazing materials are suitable as an alternative to the step for the medium / low temperature region in the step brazing.
[0023]
For example, first, when an electrode member and a thermoelectric conversion material are joined using an Au-Sn20 brazing material having a solidus temperature of about 280 ° C, as described above, the solidus temperature (remelting Temperature) of 650 ° C. or higher. Thus, the point of obtaining a joint having a high remelting temperature is that an Au-Ge-based brazing material, an Au-Si-based brazing material (solidus temperature is about 360 ° C), an Au-In-based brazing material, or a Sn-In-based brazing material. The same applies to the case of using other brazing materials, such as a brazing material, a Sn-Ag-based brazing material. Therefore, after joining is completed, another member can be brazed to, for example, an electrode member or the like without using a brazing material having the same material as the first used brazing material and melting the joined portion obtained in the first joining.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the method for assembling a thermoelectric conversion module according to the present invention will be described.
[0025]
First embodiment The thermoelectric conversion module 10 to be assembled has a structure in which n-type and p-type semiconductor chips (thermoelectric conversion materials) 11 are sandwiched between electrode members 12 as shown in FIG. The two types of semiconductor chips 11 are alternately connected via an electrode member 12 and are electrically connected in series. The arrangement of the semiconductor chip 11 and the electrode members 12 is determined so that the electrode members 12 connecting the semiconductor chips 11 are alternately positioned above and below the semiconductor chip 11. The semiconductor chip 11 used in this embodiment is made of NaCo. ₂ O ₄ The electrode member was made of Ni.
[0026]
Hereinafter, assembly of the thermoelectric conversion module of the present embodiment will be described.
[0027]
First, the prepared Ni plate material was cut to obtain a rectangular (6 mm × 14 mm × 2 mm) plate material. This is used as the electrode member 12 of the thermoelectric conversion module. Next, the semiconductor material prepared for each of the n-type and the p-type was first molded and sintered by hot pressing and cut into 50 mm × 50 mm × 8 mm. Thereafter, a Ni layer 11a having a thickness of 2 mm was formed (metalized) on the bonding surface (the widest upper and lower end surfaces) with the electrode member 12 (see FIG. 2), and the outer surface of the formed Ni layer 11a was polished smoothly. . And it cut | disconnected to 6 mm x 6 mm x 8 mm, and obtained the semiconductor chip 11 used as the other joining object.
[0028]
Further, an Au-Sn20 brazing material 13 (see FIG. 2) used for joining the semiconductor chip 11 and the electrode member 12 was manufactured. First, an ingot of 80% by weight of Au and 20% by weight of Sn was produced by melt casting, and the ingot was subjected to extrusion and rolling to obtain a foil-shaped (20 μm thick) Au-Sn20 brazing material. This was cut into a predetermined size to obtain a brazing material 13 used for joining.
[0029]
Thereafter, the semiconductor chip 11 and the electrode member 12 were joined. First, as shown in FIG. 2, the Ni—Ni 20 brazing material 13 is interposed above and below the n-type and p-type semiconductor chips 11 alternately arranged so that the joint end faces are positioned vertically. Electrode member 12 made of carbon was arranged using a jig (not shown) made of carbon. Then, the bonding portion where the brazing material 13 was interposed was heated to bond the semiconductor chip 11 and the electrode member 12, thereby obtaining the thermoelectric conversion module 10. The bonding conditions were as follows: a heating temperature of 600 ° C., a heating time of 10 minutes, and a hydrogen-containing nitrogen gas (N ₂ -3% by volume H ₂ (Gas) atmosphere. The obtained thermoelectric conversion module 10 is used, for example, by brazing (see FIG. 1) or screwing the terminal 14a of the lead wire 14 for energization.
[0030]
Second to sixth embodiments : A thermoelectric conversion module was manufactured by changing the composition ratio of the Au—Sn brazing material used in the joining process, the material of the electrode member, and the conditions for the metal sprayed (metalized) on the semiconductor chip as necessary. The other conditions are the same as those of the first embodiment, and the description is omitted. The respective conditions in each embodiment are as shown in Table 1.
[0031]
Comparative Example 1 : A thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the first embodiment. The conditions are as shown in Table 1.
[0032]
Evaluation of joints : The joint between the semiconductor chip 11 and the electrode member 12 of the thermoelectric conversion module obtained in each of the embodiments and the comparative example was sampled, and differential thermal / thermogravimetric simultaneous measurement (TG / DTA) was performed in a temperature range from room temperature to 700 ° C. ) Was performed to determine whether or not a peak (endothermic peak) associated with melting was on the DTA curve. In addition, a test piece in which electrode members 12 are joined to both ends of a semiconductor chip 11 as shown in FIG. 3 is prepared, each electrode member 12 is sandwiched between pliers, and both electrode members 12 are peeled off from the semiconductor chip 11. The joint strength was measured by pulling in the direction of arrow B. Then, those broken at the portion of the semiconductor chip (element) 11 were evaluated as “good”, and those broken at the joint part by the brazing material were evaluated as “bad”. Table 1 shows the measurement results. The remelting temperature and the bonding strength of the thermoelectric conversion module obtained in each of the embodiments and comparative examples described below were measured in the same manner.
[0033]
[Table 1]

[0034]
As shown in Table 1, in each embodiment, as a result of setting the heating temperature at the time of joining to about 330 ° C. higher than the solidus temperature (278 ° C.) of the brazing material, a high melting point of 650 ° C. or more (remelting) was obtained. Temperature). Therefore, it has been found that even if the temperature of the module becomes high when the thermoelectric conversion module is used, it is possible to prevent the joint from melting and breaking the module. Also, the bonding strength was sufficiently high and good. On the other hand, in Comparative Example 1 heated to the temperature used in the conventional brazing, it was found that a joint having a high re-melting temperature could not be obtained, and the joint might be melted at a high temperature. . As a result, it was found that a joint having a high remelting temperature and a high joint strength can be obtained by using the assembling method of the embodiment.
[0035]
Seventh to ninth embodiments : A thermoelectric conversion module was manufactured using a brazing material different from that of the first embodiment. The brazing filler metal used was an Au-Ge brazing filler metal. Further, for each of the seventh to ninth embodiments, the thermoelectric conversion module was manufactured by changing the composition ratio of the used Au-Ge brazing material, the material of the electrode member, and the conditions for the metal to be metallized on the semiconductor chip as necessary. . Other conditions were the same as in the first embodiment. The respective conditions in each embodiment are as shown in Table 2.
[0036]
Comparative Example 2 : As shown in Table 2, the thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the seventh embodiment.
[0037]
[Table 2]

[0038]
Tenth to twelfth embodiments : A thermoelectric conversion module was manufactured using a brazing material different from that of the first embodiment. The brazing material used was an Au-Si brazing material. Further, for each of the tenth to twelfth embodiments, thermoelectric conversion modules were manufactured by changing the composition ratio of the used Au-Si brazing material, the material of the electrode member, and the conditions regarding the metal to be metallized on the semiconductor chip as necessary. . Other conditions were the same as in the first embodiment. The respective conditions in each embodiment are as shown in Table 3.
[0039]
Comparative Example 3 : As shown in Table 3, the thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the tenth embodiment.
[0040]
[Table 3]

[0041]
13th to 15th embodiments : A thermoelectric conversion module was manufactured using a brazing material different from that of the first embodiment. The brazing material used was an Au-In brazing material. Further, for each of the thirteenth to fifteenth embodiments, the thermoelectric conversion module was manufactured by changing the composition ratio of the used Au-In brazing material, the material of the electrode member, and the conditions regarding the metal to be metallized on the semiconductor chip as necessary. . The other conditions were the same as in the first embodiment, although there were some differences in the heating temperature. Each condition in each embodiment is as shown in Table 4.
[0042]
Comparative Example 4 : As shown in Table 4, a thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the thirteenth embodiment.
[0043]
[Table 4]

[0044]
Sixteenth to eighteenth embodiments : A thermoelectric conversion module was manufactured using a brazing material different from that of the first embodiment. The brazing material used was a Sn-In brazing material. Further, for each of the sixteenth to eighteenth embodiments, the thermoelectric conversion module was manufactured by changing the composition ratio of the Sn—In brazing material to be used, the material of the electrode member, and the conditions regarding the metal to be metallized on the semiconductor chip as necessary. . Other conditions were the same as in the first embodiment. The conditions in each embodiment are as shown in Table 5.
[0045]
Comparative Example 5 : As shown in Table 5, the thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the sixteenth embodiment.
[0046]
[Table 5]

[0047]
19th to 21st embodiments : A thermoelectric conversion module was manufactured using a brazing material different from that of the first embodiment. The brazing material used was a Sn-Ag brazing material. Further, for each of the nineteenth to twenty-first embodiments, the thermoelectric conversion module was manufactured by changing the composition ratio of the Sn-Ag brazing material to be used, the material of the electrode member, and the conditions for the metal to be metallized on the semiconductor chip as necessary. . Other conditions were the same as in the first embodiment. The respective conditions in each embodiment are as shown in Table 6.
[0048]
Comparative Example 6 : As shown in Table 6, the thermoelectric conversion module was manufactured by changing the heating temperature conditions at the time of joining. Other conditions were the same as in the nineteenth embodiment.
[0049]
[Table 6]

[0050]
As shown in Tables 2 to 6, when a brazing material other than the Au-Sn brazing material was used, the same result as that of the Au-Sn brazing material was obtained. That is, a joint having a high melting point (remelting temperature) of 650 ° C. or more or 700 ° C. or more could be obtained. Therefore, it has been found that when the thermoelectric conversion module is heated to a high temperature, it is possible to prevent the joint from melting and breaking the module. It was also found that the bonding strength itself was sufficiently high. On the other hand, in each comparative example using the conventional brazing method, a joint having a high remelting temperature could not be obtained. And there were cases where the bonding strength was not sufficient. As a result, even with the brazing material other than the Au-Sn brazing material, if the assembling method of each embodiment is used, a bonding portion having a high remelting temperature and a high bonding strength as a bonding portion between the semiconductor chip and the electrode member. It turned out that a part was obtained.
[0051]
【The invention's effect】
As described above, if the method for assembling a thermoelectric conversion module according to the present invention is used, when joining an electrode member to, for example, a thermoelectric conversion material, by using a low melting point brazing material, and by heating at a joining temperature in a medium to low temperature region, A joint having a high remelting temperature can be obtained. If the joining temperature can be kept low, deterioration of the joining object such as a thermoelectric conversion material at the time of joining can be prevented. Further, if the re-melting temperature of the joint is high, the joint is prevented from melting when the thermoelectric conversion module is used, and the durability and reliability of the thermoelectric conversion module are improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a thermoelectric conversion module.
FIG. 2 is a side view of the joining structure of the thermoelectric conversion module in the direction of arrow A in FIG.
FIG. 3 is a side view showing a test piece of bonding strength.
[Explanation of symbols]
10. Thermoelectric conversion module
11 Semiconductor chips (thermoelectric conversion materials and other objects to be joined)
11a Ni layer (metal layer formed by metallization)
12 electrode members
13 Brazing filler metal

Claims

複数の熱電変換材料が電極部材を介して電気的に直列接続されてなる熱電変換モジュールの組立方法であり、電極部材をろう材を用いて接合対象物に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、
前記電極部材の接合面と前記接合対象物の接合面との間に低融点のろう材を介在させ、この状態でろう材が介在される接合位置をろう材の固相線温度より１５０℃〜５３０℃高い温度に加熱してろう材と電極部材との間で液相拡散を生じさせて電極部材と接合対象物とを接合する工程を有することを特徴とする熱電変換モジュールの組立方法。A method for assembling a thermoelectric conversion module in which a plurality of thermoelectric conversion materials are electrically connected in series via an electrode member, the method including assembling a thermoelectric conversion module including a step of joining an electrode member to an object to be joined using a brazing material. In the method,
A low melting point brazing material is interposed between the joining surface of the electrode member and the joining surface of the object to be joined, and in this state, the joining position where the brazing material is interposed is set at 150 ° C. or higher than the solidus temperature of the brazing material. A method for assembling a thermoelectric conversion module, comprising a step of heating a temperature higher by 530 ° C. to cause a liquid phase diffusion between a brazing material and an electrode member to join the electrode member and an object to be joined.

接合面間に介在させるろう材は、Ａｕ−Ｓｎ系、Ａｕ−Ｇｅ系、Ａｕ−Ｓｉ系、Ａｕ−Ｉｎ系、Ｓｎ−Ｉｎ系、Ｓｎ−Ａｇ系のろう材である請求項１に記載の熱電変換モジュールの組立方法。The brazing material interposed between the joining surfaces is an Au-Sn-based, Au-Ge-based, Au-Si-based, Au-In-based, Sn-In-based, or Sn-Ag-based brazing material according to claim 1. How to assemble thermoelectric conversion modules.

電極部材は、Ａｌ、Ｃｒ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｎｂ、Ｍｏ、Ｉｎ、Ｔａ、Ｗ、Ｉｒ、Ｐｔ、Ａｕ、Ｐｄ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である請求項１または請求項２に記載の熱電変換モジュールの組立方法。The electrode member is a pure metal selected from Al, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, In, Ta, W, Ir, Pt, Au, and Pd, or two or more of these. The method for assembling a thermoelectric conversion module according to claim 1 or 2, wherein the alloy is an alloy made of the metal described in (1).

電極部材と接合される接合対象物は熱電変換材料である請求項１から請求項３のいずれか一項に記載の熱電変換モジュールの組立方法。The method for assembling a thermoelectric conversion module according to any one of claims 1 to 3, wherein the object to be joined to the electrode member is a thermoelectric conversion material.

熱電変換材料は、その接合面に、Ａｌ、Ｃｒ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｎｂ、Ｍｏ、Ｉｎ、Ｔａ、Ｗ、Ｉｒ、Ｐｔ、Ａｕ、Ｐｄから選択される純金属、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ものである請求項４に記載の熱電変換モジュールの組立方法。The thermoelectric conversion material has, on its bonding surface, a pure metal selected from Al, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, In, Ta, W, Ir, Pt, Au, and Pd. The method for assembling a thermoelectric conversion module according to claim 4, wherein the alloy comprising two or more metals is metallized.