JP4385484B2 - Multilayer ceramic substrate manufacturing method and copper-based conductive paste - Google Patents

Description

【００９４】
焼成工程における酸素分圧は、表１に示すように、昇温過程では３つの温度領域に分けてそれぞれ設定され、かつ降温過程においても所定の値に設定された。たとえば、試料１について言えば、酸素分圧は、２５〜７００℃の昇温過程では、２０ｍｍＨｇに設定され、７００〜９００℃の昇温過程では、１０ｍｍＨｇに設定され、９００〜１０００℃の昇温過程では、１０^-3ｍｍＨｇに設定され、１０００〜２５℃の降温過程では、１０^-6ｍｍＨｇに設定された。
【００９５】
また、表１の「クラック」および「反り」の各欄において、「○」はこれらクラックまたは反りが生じなかったことを示し、「×」はこれらクラックまたは反りが生じたことを示している。また、「導体膜状態」の欄において、「Ｃｕ」は導体膜がＣｕを主成分としていることを示し、「Ｃｕ₂ Ｏ」は導体膜がＣｕ₂ Ｏを主成分としていることを示している。
【００９６】
表１に示した試料において、試料２および４〜６が、焼成時の雰囲気条件に関して好ましい範囲内にあるものである。これら試料２および４〜６によれば、クラックや反りがなく、また、導体膜において、Ｃｕが生成された、多層セラミック基板を得ることができた。
【００９７】
これに対して、試料１では、２５〜７００℃の昇温過程における酸素分圧が１０^-6ｍｍＨｇ〜１０ｍｍＨｇといった好ましい範囲を外れて高すぎたため、Ｃｕ₂ Ｏは体積膨張を伴ってＣｕＯへと酸化され、得られた多層セラミック基板においてクラックを発生した。
【００９８】
また、試料３においては、７００〜９００℃の昇温過程における酸素分圧が、１０^-4ｍｍＨｇ〜１０ｍｍＨｇといった好ましい範囲から外れて高すぎたため、基体用グリーンシートにおける低温焼結セラミック材料の焼結が開始する前に、Ｃｕ₂ Ｏは体積膨張を伴ってＣｕＯへと酸化され、得られた多層セラミック基板においてクラックを発生した。
【００９９】
また、試料７においては、９００〜１０００℃の昇温過程において、酸素分圧が、１０^-3ｍｍＨｇ以下といった好ましい範囲を外れて高すぎたため、Ｃｕ₂ ＯからＣｕへの十分な還元が生じず、そのため、導体膜において、表面のみがＣｕに還元されたが、内部ではＣｕ₂ Ｏが残存した。また、基体用グリーンシートにおける低温焼結セラミック材料の焼結が進行しているにも関わらず、Ｃｕ₂ Ｏから収縮を伴うＣｕへの十分な還元が生じないために、導電性ペースト体における収縮が生じず、そのため、得られた多層セラミック基板において反りが発生した。
【０１００】
また、試料８では、１０００〜２５℃の降温過程において、酸素分圧を１０^-3ｍｍＨｇというように、比較的高く設定したので、昇温過程の最終段階で、導体膜にＣｕを生成していたにも関わらず、導体膜の表面においてＣｕがＣｕ₂ ＯおよびＣｕＯとなるように酸化されたものと考えられる。
【０１０１】
【実験例２】
実験例２は、銅系導電性ペーストにおけるＣｕ₂ Ｏの粒径についての好ましい範囲を求めようとするもので。る。
【０１０２】
表１における試料２の場合と同様の操作を実施しながら、銅系導電性ペーストについては表２に示すような種々の平均粒径のＣｕ₂ Ｏ粉末を用い、試料となる多層セラミック基板を得た。なお、表２において、平均粒径は、マイクロトラック粒度分布計によるＤ５０の値をもって示したものである。
【０１０３】
また、表２に示した「印刷性」は、スクリーン印刷による印刷が良好に行なえたかどうか、ペースト化が容易であったかどうか、ビアホール導体のための貫通孔への導電性ペーストの埋め込み状態が良好であったかどうかを評価したものであり、また、「焼成後状態」は、導電性ペースト体の焼成によって得られた配線導体、特にビアホール導体の状態を評価したものである。
【０１０４】
【表２】

【０１０５】
表２に示した試料において、試料１２〜１７については、Ｃｕ₂ Ｏの平均粒径が０．５〜１０μｍといった好ましい範囲内にあり、その含有量を５０〜９０重量％とすることにより、良好な印刷性を示すとともに、焼成後において良好な配線導体を形成することができた。
【０１０６】
これに対して、試料１１では、Ｃｕ₂ Ｏの平均粒径が０．５μｍより小さいため、有機ビヒクルの含有量を５０重量％にまで上げても、ペースト化することが困難であり、また、焼成後のビアホール導体において隙間が発生した。
【０１０７】
また、試料１８では、Ｃｕ₂ Ｏの平均粒径が１０μｍより大きいため、貫通孔内への導電性ペーストの埋め込み状態が不良となり、また、焼成後の配線導体において導通不良が生じた。
【０１０８】
【実験例３】
実験例３は、銅系導電性ペーストにおけるＣｕ₂ Ｏ以外の添加物の添加による特性改善効果を評価しようとするものである。
【０１０９】
実験例１の場合と同様のＢａ−Ｓｉ−Ａｌ−Ｂ−Ｃａ−Ｏ系低温焼結セラミック材料を含むセラミックグリーンシートを用意し、その上に、表３に示した種々の組成の銅系導電性ペーストを付与して導電性ペースト膜を形成し、表１における試料２の場合と同様の雰囲気条件を適用して、焼成工程に付し、各試料を得た。
【０１１０】
なお、この実験例３において、表３に示した「Ｃｕ₂ Ｏ」については、平均粒径が０．５μｍのものを用い、「Ｃｕ」および「ＣｕＯ」については、平均粒径が２μｍのものを用い、「ガラス」としては、軟化点８２０℃のホウケイ酸バリウム系ガラスフリットを用い、「セラミック」としては、上述したセラミックグリーンシートに含まれる低温焼結セラミック材料と同様のＢａ−Ｓｉ−Ａｌ−Ｂ−Ｃａ−Ｏ系セラミックであって焼結温度が１０００℃のものを用い、「金属」としては、モリブデンを用いた。
【０１１１】
また、これら銅系導電性ペーストに係る各試料について、反り、導体膜密着強度、めっき性・半田付け性、およびシート抵抗値をそれぞれ評価した。
【０１１２】
反りについては、４インチ平方で厚み０．６ｍｍのセラミック板となるセラミックグリーンシートの表面に占有面積８０％および膜厚１５μｍとなるように銅系導電性ペーストをもって導電性ペースト膜を形成し、焼成後のセラミック板において発生した反りの絶対値を評価した。この反りが５０μｍ未満であるとき、使用上問題ないと評価できる。
【０１１３】
導体膜密着強度については、２ｍｍ×２ｍｍの導体膜をセラミック板上に形成した試料を得るため、セラミックグリーンシート上に導電性ペースト膜を形成したものを焼成し、焼成後において、導体膜にＬ字リード線を半田付けした状態として、引っ張り強度試験を実施して、導体膜が剥がれた時点での引っ張り強度を示したものである。この導体膜密着強度が２ｋｇｆ／２×２ｍｍ² を超えるとき、使用上問題ないと評価できる。
【０１１４】
めっき性については、試料となる銅系導電性ペーストによって形成された導体膜上にニッケルめっきを施し、このめっき膜の析出状態を評価したものである。
【０１１５】
半田濡れ性については、試料となる銅系導電性ペーストを用いて形成された導体膜を共晶半田に浸漬し、半田の付着状態を評価したものである。
【０１１６】
シート抵抗値については、試料となる銅系導電性ペーストを用いて、ライン幅１００μｍ厚み１５μｍの導体膜を形成し、そのシート抵抗値を評価したものである。このシート抵抗値が３．０ｍΩ／□未満のとき、使用上問題ないと評価できる。
【０１１７】
【表３】

【０１１８】
表３に示した試料において、試料２１については、Ｃｕ₂ Ｏ以外の添加物が添加されず、試料２２〜３４については、Ｃｕ₂ Ｏ以外に何らかの添加物が添加されている。
【０１１９】
これらの添加物の内、ＣｕおよびＣｕＯについては、６０重量％以下であることが好ましいが、試料３１および３２については、６０重量％の上限を超えている。そのため、試料３１および３２については、反りが大きく生じ、特に試料３２においては、反りが極めて大きく、また、めっき性・半田濡れ性が悪く、シート抵抗値も３．０ｍΩ／□以上となっている。
【０１２０】
また、添加物としてのガラス、セラミックおよび金属については、５重量％以下の含有量であることが好ましい。これに関して、試料３３および３４については、この５重量％の上限を超えている。そのため、試料３３においては、めっき性・半田濡れ性が悪く、また、シート抵抗値も４．５ｍΩ／と高くなっている。また、試料３４では、導体膜密着強度が１．８ｋｇｆ／２×２ｍｍ² と低くなっている。
【０１２１】
【発明の効果】
以上のように、この発明によれば、多層セラミック基板を得るために焼成される生の積層体において、低温焼結セラミック材料を含む、複数の積層された基体用グリーンシートと、これら基体用グリーンシートの間の界面に沿って配置されかつ収縮抑制用無機材料を含む、収縮抑制用無機材料層と、配線導体を形成するため、基体用グリーンシートに関連してＣｕ₂ Ｏを含む銅系導電性ペーストを付与することによって形成された導電性ペースト体とを備えるようにしており、この生の積層体を焼成する工程において、収縮抑制用無機材料層によって基体用グリーンシートの主面方向での収縮を抑制しながら、低温焼結セラミック材料を焼結させるとともに、導電性ペースト体に含まれるＣｕ₂ ＯをＣｕに還元することによって配線導体を形成するようにしているので、基体用グリーンシートと導電性ペースト体との間において収縮挙動を近似させることが可能となり、配線導体に関連してクラックや隆起や隙間のない状態で多層セラミック基板を製造することができる。
【０１２２】
したがって、小型化かつ配線の高密度化が図られた多層セラミック基板を、高い信頼性をもって製造することができる。
【０１２３】
また、この発明によれば、焼成工程において、２００℃から７００℃までの昇温過程では、Ｃｕ₂ＯがＣｕＯに酸化されたりＣｕに還元されたりしない１０^-6ｍｍＨｇ〜１０ｍｍＨｇの酸素分圧を有する雰囲気が与えられ、７００℃から低温焼結セラミック材料の収縮開始温度までの昇温過程では、Ｃｕ₂ＯがＣｕＯに酸化されたりＣｕに還元されたりしない１０^-4ｍｍＨｇ〜１０ｍｍＨｇの酸素分圧を有する雰囲気が与えられ、低温焼結セラミック材料の収縮開始温度から１０００℃までの昇温過程では、Ｃｕ₂ＯがＣｕに還元される１０^-3ｍｍＨｇ以下の酸素分圧を有する雰囲気が与えられるので、上述したような収縮挙動をより確実に近似させることができる。
【０１２４】
また、上述のように酸素分圧を規定することにより、脱バインダが生じる温度領域では、Ｃｕ₂ ＯがＣｕＯに酸化されない程度にまで酸化性雰囲気を与えることができるので、基体用グリーンシートや導電性ペースト体に対する脱バインダを容易にし、焼成時間の短縮を図ることができるとともに、得られた多層セラミック基板においてカーボン成分の残渣を減らすことができ、したがって、密度が高くかつ信頼性により優れた多層セラミック基板を得ることができる。
【０１２５】
上述した焼成工程における１０００℃から２００℃までの降温過程において、１０^-6ｍｍＨｇ以下の酸素分圧を有する雰囲気が与えられると、昇温過程の最終段階で、配線導体にＣｕを生成していたのも関わらず、降温過程において、ＣｕがＣｕ₂ＯまたはＣｕＯに酸化されることを確実に防止することができる。したがって、このような降温過程での酸素分圧の制御は、特に、焼成されるべき生の積層体の外表面上に導電性ペースト膜を形成している場合に、顕著な効果を発揮する。
【０１２６】
また、この発明において用いられる銅系導電性ペーストが、５０〜９０重量％の有機ビヒクルとを含み、無機成分の主成分として、平均粒径が０．５〜１０μｍであって、最大粒径が５０μｍ以下のＣｕ₂ Ｏを含むようにすれば、ビアホール導体のための貫通孔内への導電性ペーストの充填を良好に行なうことができ、したがって、焼成後において、隙間や導通不良のないビアホール導体を確実に形成することができる。
【０１２７】
また、銅系導電性ペーストにおいて、上述の無機成分の主成分であるＣｕ₂ Ｏが４０重量％以上含むようにしながら、平均粒径２〜１０μｍのＣｕおよびＣｕ₂ Ｏの少なくとも一方を６０重量％以下含むようにしたり、軟化点８００〜９５０℃のガラスフリットもしくはガラスビーズ、低温焼結セラミック材料、および、融点１１００℃以上の金属もしくはその金属レジネートから選ばれる少なくとも１種の添加物を、５重量％以下含ませることによって、配線導体の抵抗値をあまり上げることなく、導電性ペースト体の焼成時の収縮挙動の微調整を行なったり、導電性ペースト体を焼成して得られた配線導体と基体用グリーンシートを焼成して得られたセラミック層との界面での接合力を向上させたりすることができる。
【０１２８】
そのため、得ようとする多層セラミック基板の設計において、配線導体の分布密度の片寄りを懸念することなく、自由に電子回路を組むことができる。また、得られた多層セラミック基板の高周波特性を低下させることがなく、反りを生じさせず、信頼性かつ位置精度に優れた配線導体を形成することができる。
【図面の簡単な説明】
【図１】この発明の一実施形態による多層セラミック基板の製造方法において作製される生の積層体１を図解的に示す断面図である。
【符号の説明】
１ 生の積層体
２ 基体用グリーンシート
３ 収縮抑制用無機材料層
４ 導電性ペースト体
５ 導電性ペースト膜
６ 導電性ペースト柱[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a multilayer ceramic substrate, and more particularly to a method for producing a multilayer ceramic substrate having a wiring conductor mainly composed of copper and a copper-based conductive paste advantageously used in this method. .
[0002]
[Prior art]
The multilayer ceramic substrate includes a plurality of laminated ceramic layers. Various types of wiring conductors are provided on such a multilayer ceramic substrate. As a wiring conductor, for example, an internal conductor film extending along a specific interface between ceramic layers is formed inside a multilayer ceramic substrate, a via-hole conductor extending so as to penetrate a specific ceramic layer is formed, or An external conductor film extending on the outer surface of the multilayer ceramic substrate is formed.
[0003]
The multilayer ceramic substrate is used for mounting semiconductor chip components and other chip components and wiring these electronic components to each other. The wiring conductor described above provides an electrical path for this interconnection.
[0004]
In addition, passive components such as capacitor elements and inductor elements may be incorporated in the multilayer ceramic substrate. In such a case, the internal conductor film as the wiring conductor and a part of the via-hole conductor are used to configure these passive components.
[0005]
In order to increase the functionality, density, and performance of a multilayer ceramic substrate, it is effective to arrange the wiring conductors as described above at a high density.
[0006]
However, in order to obtain a multilayer ceramic substrate, a firing process must be performed. In such a firing process, shrinkage occurs due to ceramic sintering, and this shrinkage occurs uniformly throughout the multilayer ceramic substrate. Therefore, undesired deformation and distortion may occur in the wiring conductor. Such deformation and distortion in the wiring conductor inhibits the above-described increase in the density of the wiring conductor.
[0007]
Therefore, in manufacturing a multilayer ceramic substrate, it has been proposed to apply a so-called non-shrink process that can substantially prevent shrinkage in the main surface direction of the multilayer ceramic substrate in the firing step.
[0008]
In the method for producing a multilayer ceramic substrate by a non-shrinking process, a green sheet for a substrate including a low-temperature sintered ceramic material that can be sintered at a temperature of, for example, 1000 ° C. or less is prepared, and the above-mentioned low-temperature sintered ceramic material is sintered. An inorganic material for suppressing shrinkage that does not sinter at the sintering temperature is prepared. And in producing the raw laminated body provided with the several laminated | stacked green sheet | seat for base | substrates, the inorganic material for shrinkage | contraction suppression containing the above-mentioned inorganic material for shrinkage | contraction suppression along the interface between several green sheet | seats for base | substrates The shrinkage-suppressing inorganic material layer is formed on the main surface of the specific base green sheet so that the material layer is disposed.
[0009]
Moreover, in order to form a wiring conductor in the stage before laminating | stacking the green sheet for base | substrates, providing a conductive paste in relation to the green sheet | seat for base | substrates is performed. More specifically, in order to form an inner conductor film or an outer conductor film, a conductive paste film is formed on the surface of the green sheet for substrate or the inorganic material layer for shrinkage suppression, and in order to form a via-hole conductor, A conductive paste column is formed by providing a through hole so as to penetrate the green sheet for use and, if necessary, the inorganic material layer for shrinkage suppression, and filling the through hole with the conductive paste.
[0010]
The raw laminate obtained as described above is then fired. In this firing step, a reaction layer having a thickness of about 2 to 3 μm is formed at the interface between the green sheet for substrate and the inorganic material layer for suppressing shrinkage, and this reaction layer bonds the green sheet for substrate and the inorganic material layer for suppressing shrinkage. Acts like In addition, since the shrinkage-inhibiting inorganic material is not substantially sintered, shrinkage does not substantially occur in the shrinkage-inhibiting inorganic material layer. For this reason, the inorganic material layer for suppressing shrinkage restrains the green sheet for the substrate, whereby the green sheet for the substrate substantially shrinks only in the thickness direction, but shrinkage in the main surface direction is suppressed. The As a result, non-uniform deformation is less likely to occur in the multilayer ceramic substrate obtained by firing the raw laminate, and therefore, it is possible to prevent undesirable deformation and distortion in the wiring conductor, High density wiring conductors are possible.
[0011]
On the other hand, the conductive paste used to form the wiring conductor as described above contains a metal powder as a conductive component and an organic vehicle composed of a binder and a solvent, and is fired simultaneously with the firing of the ceramic. Thus, a wiring conductor having a desired form is formed. As a metal constituting the wiring conductor, a metal having copper as a main component is used because it has a low resistance, hardly causes migration, and can provide high reliability.
[0012]
[Problems to be solved by the invention]
In the step of firing the raw laminate described above, a reaction layer that exerts an adhesive action between the green sheet for substrate and the inorganic material layer for suppressing shrinkage is generated because glass is generated on the green sheet for substrate. Alternatively, it is from a temperature range in which the glass component previously contained therein is softened, for example, at a relatively high temperature of about 800 to 900 ° C.
[0013]
On the other hand, in the above-described firing step, the conductive paste also undergoes sintering, thereby causing shrinkage. The temperature at which such shrinkage starts is usually the low-temperature sintered ceramic material contained in the green sheet for the substrate. The sintering shrinkage start temperature is about 100 to 200 ° C. on the low temperature side, and therefore, when the sintering shrinkage of the conductive paste starts, the reaction layer having the above-mentioned adhesive action has not yet been formed, The effect | action which suppresses the shrinkage | contraction of the main surface direction by the inorganic material layer for shrinkage | contraction suppression does not work.
[0014]
Therefore, the conductive paste shrinks without being constrained by the shrinkage inhibiting action of the shrinkage inhibiting inorganic material layer in the firing step. Therefore, the shrinkage that occurs in the conductive paste body is larger in the main surface direction and smaller in the thickness direction than the green sheet side for the substrate.
[0015]
Thus, since the shrinkage behavior in the firing process, more specifically, the timing and amount of shrinkage and the direction of main shrinkage are different between the conductive paste body and the green sheet for the substrate, the obtained multilayer ceramic In the substrate, warpage, cracks, bumps, gaps and the like may occur. In particular, cracks, bumps and gaps are likely to occur in connection with conductive paste columns that are to be via-hole conductors.
[0016]
For example, cracks are likely to occur in the vicinity of the via-hole conductor in the ceramic layer as the conductive paste pillar partially compresses the green sheet for the substrate. Further, since the degree of shrinkage in the thickness direction of the conductive paste body is smaller than that of the green sheet for the substrate, the bulge is likely to occur at or near the via-hole conductor in the obtained multilayer ceramic substrate. Further, the gap is likely to occur at the interface between the ceramic layer and the via hole conductor or inside the via hole conductor.
[0017]
In addition, in order to make the shrinkage behavior of the conductive paste body in the firing process close to the shrinkage behavior of the green sheet for the substrate, it is possible to add a non-sinterable inorganic substance, high softening point glass, etc. to the conductive paste. In such a case, not only does the resistance value of the obtained wiring conductor increase, but also the total shrinkage amount through the firing process is reduced, and thus the above-described crack and bulge problems cannot be solved. .
[0018]
Accordingly, an object of the present invention is to provide a method for manufacturing a multilayer ceramic substrate and a conductive paste advantageously used in this method, which can solve the above-described problems.
[0019]
[Means for Solving the Problems]
In order to solve the above-described technical problem, a method for manufacturing a multilayer ceramic substrate according to the present invention includes a step of preparing a low-temperature sintered ceramic material that can be sintered at a temperature of 1000 ° C. or lower, A step of preparing an inorganic material for shrinkage suppression that does not sinter at the sintering temperature, and Cu for providing a conductor mainly composed of copper₂And a step of preparing a copper-based conductive paste containing O.
[0020]
Next, a plurality of laminated base green sheets including a low-temperature sintered ceramic material, and an inorganic material for shrinkage suppression disposed along an interface between the plurality of base green sheets and including an inorganic material for shrinkage suppression A raw laminate is produced comprising a layer and a conductive paste formed by applying a copper-based conductive paste in association with the green sheet for the substrate to form a wiring conductor.
[0021]
The raw laminate is then fired. In this firing step, the low-temperature sintered ceramic material is sintered while suppressing the shrinkage in the main surface direction of the green sheet for the substrate by the shrinkage-inhibiting inorganic material layer, and Cu contained in the conductive paste body₂A wiring conductor is formed by reducing O to Cu.
[0022]
  In the firing process described above2In the temperature raising process from 00 ° C. to 700 ° C., Cu₂O is not oxidized to CuO or reduced to Cu 10^-6An atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is given, and in the temperature rising process from 700 ° C. to the shrinkage start temperature of the low-temperature sintered ceramic material,₂O is not oxidized to CuO or reduced to Cu 10^-FourAn atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is given, and in the temperature raising process from the shrinkage start temperature of the low-temperature sintered ceramic material to 1000 ° C., Cu₂O is reduced to Cu 10^-3An atmosphere having an oxygen partial pressure of mmHg or less is provided.
[0023]
  GoodPreferably, in the above-described firing step, Cu is Cu in the temperature lowering process from 1000 ° C. to 200 ° C.₂Not oxidized to O or CuO 10^-6An atmosphere having an oxygen partial pressure of mmHg or less is provided.
[0024]
In the present invention, the low-temperature sintered ceramic material can be a composition containing a mixture of glass and ceramic, or can be a composition that produces glass in the firing step.
[0025]
The conductive paste body described above is a conductive paste film for a conductor film extending along the main surface of the base green sheet, or a via hole conductor extending so as to penetrate the base green sheet. It may be a conductive paste column.
[0026]
The present invention is also directed to a copper-based conductive paste that is advantageously used in the method for manufacturing a multilayer ceramic substrate as described above. This copper-based conductive paste includes 50 to 90% by weight of an inorganic component and 10 to 50% by weight of an organic vehicle, and has an average particle size of 0.5 to 10 μm as a main component of the inorganic component, Cu having a particle size of 50 μm or less₂It is characterized by containing O.
[0027]
In the inorganic component contained in the copper-based conductive paste described above, Cu₂It is preferable to contain 40% by weight or more of O.
[0028]
Moreover, in this inorganic component, 60 weight% or less of at least one of Cu and CuO with an average particle diameter of 2-10 micrometers may be included.
[0029]
In addition, the inorganic component includes 5 weight% of at least one additive selected from glass frit or glass beads having a softening point of 800 to 950 ° C., low-temperature sintered ceramic material, and a metal having a melting point of 1100 ° C. or higher or a metal resinate thereof. % Or less may be included.
[0030]
Such a copper-based conductive paste is particularly advantageously used for forming conductive paste pillars for via-hole conductors.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing a raw laminate 1 produced by a method for producing a multilayer ceramic substrate according to an embodiment of the present invention.
[0032]
The raw laminate 1 forms a plurality of laminated substrate green sheets 2, a shrinkage-suppressing inorganic material layer 3 disposed along an interface between the plurality of substrate green sheets 2, and a wiring conductor. For this reason, a conductive paste body 4 formed by applying a copper-based conductive paste in association with the base green sheet 2 is provided. The conductive paste body 4 includes a conductive paste film 5 for an internal conductor film or an external conductor film extending along the main surface of the base green sheet 2, the base green sheet 2, and, if necessary, for shrinkage suppression. And a conductive paste column 6 for a via-hole conductor extending so as to penetrate the inorganic material layer 3.
[0033]
The base green sheet 2 described above includes a low-temperature sintered ceramic material that can be sintered at a temperature of 1000 ° C. or lower. The base green sheet 2 can be produced, for example, as follows.
[0034]
That is, an organic vehicle composed of an organic binder and a solvent and a plasticizer are added to a low-temperature sintered ceramic material, and a slurry is prepared by mixing them. Next, the slurry is formed into a sheet shape on a carrier film by a doctor blade method and dried to obtain a green sheet for a substrate.
[0035]
As a low-temperature sintered ceramic material, for example, a material having a composition that generates glass in a firing process, such as a mixture of barium oxide, silicon oxide, alumina, calcium oxide, and boron oxide can be used. Alternatively, for example, a ceramic that serves as a filler such as alumina and a glass that acts as a sintering aid such as borosilicate glass or silicon oxide can be used. In any case, as a low-temperature sintered ceramic material, any composition may be used as long as the ceramic composition is not reduced even when fired in a reducing atmosphere at a temperature of 1000 ° C. or lower. May be.
[0036]
Moreover, as an organic binder, an acrylic resin, polyvinyl butyral, a methacryl resin etc. can be used, for example.
[0037]
As the solvent, for example, alcohols such as toluene and isopropyl alcohol, butanol, methyl ethyl ketone and the like can be used.
[0038]
As the plasticizer, for example, di-n-butyl phthalate can be used.
[0039]
The inorganic material layer 3 for shrinkage suppression includes an inorganic material for shrinkage suppression that does not sinter at the sintering temperature of the low-temperature sintered ceramic material as described above. As this shrinkage-inhibiting inorganic material, for example, alumina or zirconia can be used.
[0040]
The inorganic material layer for shrinkage suppression 3 produces an inorganic material slurry by adding an organic vehicle and a plasticizer made of an organic binder and a solvent to the shrinkage-inhibiting inorganic material, and mixing them. It can be formed by applying to the surface of the green substrate sheet 2 and drying.
[0041]
In addition, in order to form the inorganic material layer 3 for shrinkage | contraction suppression, you may make it shape | mold an inorganic material sheet using the inorganic material slurry mentioned above, and this may be piled up on the green sheet 2 for base | substrates. Alternatively, first, the inorganic material layer 3 for suppressing shrinkage may be formed on the carrier film, and a slurry containing a low-temperature sintered ceramic material may be applied thereon to form the green sheet 2 for the substrate.
[0042]
As the organic vehicle and the plasticizer contained in the inorganic material slurry described above, the same materials as those contained in the slurry prepared in forming the green sheet 2 for a substrate can be used.
[0043]
The copper-based conductive paste constituting the conductive paste body 4 is Cu₂It contains O powder and an organic vehicle, and is obtained, for example, by stirring and kneading with a stirring crusher or three rolls.
[0044]
Regarding the organic vehicle contained in the copper-based conductive paste described above, ethyl cellulose, alkyd resin, acrylic resin, polyvinyl butyral, methacrylic resin, etc. can be used as the binder, and terpineol, butyl carbitol, butyl carbylene are used as the solvent. Tall acetate, alcohols, etc. can be used.
[0045]
The copper-based conductive paste is preferably Cu having an average particle size of 0.5 to 10 μm and a maximum particle size of 50 μm or less.₂The composition contains 50 to 90% by weight of an inorganic component mainly containing O and 10 to 50% by weight of an organic vehicle. At this time, in the inorganic component, Cu as the main component₂O is preferably contained in an amount of 40% by weight or more.
[0046]
As mentioned above, Cu₂The maximum particle size of O is set to 50 μm or less. When the maximum particle size is larger than this, it becomes difficult to completely fill the through-hole forming the via-hole conductor with the conductive paste. This is because conduction failure may occur in the conductor.
[0047]
Cu₂The reason why the average particle size of O is in the range of 0.5 to 10 μm is as follows. That is, when the average particle size is smaller than 0.5 μm, the amount of the organic vehicle necessary for pasting becomes too large, the viscosity of the paste increases, and not only makes pasting difficult, but also Cu₂This is because it is difficult to increase the O content, and gaps may be generated after firing. On the other hand, when the average particle size is larger than 10 μm, it is difficult to fill the via hole forming the via hole conductor with the conductive paste, and as a result, poor conduction tends to occur in the via hole conductor.
[0048]
Further, in the copper-based conductive paste, as an inorganic component, Cu₂The reason why O is contained in an amount of 40% by weight or more and such an inorganic component is contained in an amount of 50 to 90% by weight is to prevent a gap or poor conduction particularly in a via-hole conductor after firing. .
[0049]
Cu used in copper-based conductive paste₂As the O powder, a powder having a substantially spherical sharp particle size distribution, a particle having a mountain having a different central particle diameter in the particle size distribution, or two or more kinds of powders having different shapes such as flat powders are blended. It may be a thing.
[0050]
The viscosity of the copper-based conductive paste is preferably selected from 50 to 300 Pa · s, for example, in consideration of printability.
[0051]
Moreover, the inorganic component contained in the copper-based conductive paste may contain 60% by weight or less of at least one of Cu and CuO having an average particle diameter of 2 to 10 μm.
[0052]
Such addition of Cu has the effect of suppressing sintering shrinkage of the copper-based conductive paste, improving the effective area of the obtained conductor film, improving the density of the wiring conductor, and reducing the resistance value of the wiring conductor. is there. However, since Cu is not reduced in the firing step, shrinkage does not occur. Therefore, when Cu is contained in an amount exceeding 60% by weight, the conductive paste body 4 and the green sheet 2 for the substrate formed with the Cu do not shrink. As a result, the shrinkage behavior of the multilayer ceramic substrate may be warped.
[0053]
On the other hand, the addition of CuO has the effect of improving the adhesion strength with the ceramic layer provided by the green sheet 2 for the substrate, but if it is contained in excess of 60% by weight, it is difficult to reduce in the firing step, In the obtained multilayer ceramic substrate, it may be warped in the opposite direction to the case of adding Cu described above, and the plating property and solder wettability of the obtained conductor film may be lowered.
[0054]
The inorganic component contained in the copper-based conductive paste includes glass frit or glass beads having a softening point of 800 to 950 ° C., a low-temperature sintered ceramic material contained in the base green sheet 2, and a metal having a melting point of 1100 ° C. or higher. It may contain 5% by weight or less of at least one additive selected from the metal resinate.
[0055]
The addition of the glass frit or glass beads or the low-temperature sintered ceramic material described above has the effect of bringing the shrinkage behavior of the conductive paste body 4 closer to the shrinkage behavior of the green sheet 2 for the substrate in the firing step, and the conductive paste body 4. In the case of adding more than 5% by weight, the resistance value of the obtained wiring conductor becomes so high that it cannot be ignored. When a multilayer ceramic substrate is used in a high frequency circuit, the high frequency characteristics may be deteriorated.
[0056]
On the other hand, the addition of the above-described metal or its metal resinate suppresses the shrinkage of the conductive paste body 4 without causing much increase in the resistance value of the obtained wiring conductor, and shrinks between the green sheet 2 for the substrate. It has the effect of approximating the rate, but if added over 5% by weight, the resistance value in the wiring conductor is increased to a level that cannot be ignored, and the adhesive strength with the ceramic layer is reduced. May bring. As the metal having a melting point of 1100 ° C. or higher, for example, tungsten, molybdenum, nickel, or the like can be used.
[0057]
Depending on the configuration of the wiring conductor to be formed on the multilayer ceramic substrate, the area of the conductor film, etc., it may be necessary to finely adjust the shrinkage behavior during firing of the conductive paste body 4, or the wiring conductor and the ceramic layer It may be necessary to further improve the bonding strength at the interface. Further, when the conductive paste film 5 is formed, the copper-based conductive paste is desired to have excellent screen printability.
[0058]
In such a case, as described above, as an inorganic component contained in the copper-based conductive paste, Cu₂In addition to O, Cu and / or CuO is added, a glass frit or glass bead having a softening point of 800 to 950 ° C., a low-temperature sintered ceramic material, and / or a metal having a melting point of 1100 ° C. or higher or a metal resinate thereof is added. By doing so, it is possible to improve characteristics such as the fine adjustment of the shrinkage behavior, the improvement of the bonding force, and the improvement of the screen printability as described above.
[0059]
As the organic vehicle contained in the copper-based conductive paste, the same one as that contained in the slurry prepared at the time of forming the green sheet for substrate 2 described above can be used.
[0060]
Next, after forming the conductive paste body 4 such as the conductive paste film 5 and the conductive paste column 6 using such a copper-based conductive paste, the carrier film is peeled off, and a plurality of green substrates By laminating the sheets 2, a raw laminate 1 as shown in FIG. 1 is obtained. The details will be described below.
[0061]
As described above, when a plurality of substrate green sheets 2 are laminated, as can be seen from the form of the raw laminate 1 shown in FIG. 1, except for the uppermost substrate green sheet 2 (A), A plurality of substrate green sheets 2 are laminated in a state where the shrinkage-suppressing inorganic material layer 3 is formed on each one main surface.
[0062]
In addition, the process of forming the conductive paste body 4 such as the conductive paste film 5 and the conductive paste pillar 6 is performed at a stage before the plurality of base green sheets 2 are laminated.
[0063]
That is, a through hole for providing the conductive paste pillar 6 is provided so as to penetrate the base green sheet 2 and the shrinkage suppressing inorganic material layer 3. In the uppermost substrate green sheet 2 (A), a through hole is provided so as to penetrate the substrate green sheet 2 (A).
[0064]
Then, a copper-based conductive paste is printed on each of the inorganic material layer 3 for suppressing shrinkage and the green sheet 2 (A) for base by, for example, a screen printing method, thereby forming the conductive paste film 5. At the same time, the copper-based conductive paste is filled in the through holes, and the conductive paste columns 6 are formed.
[0065]
The conductive paste film 5 and the conductive paste column 6 may be formed at the same time as described above, but the characteristics required for the copper-based conductive paste are those for the conductive paste film 5. If different from the one for the conductive paste pillar 6, for each contained Cu₂You may make it form in another process, aiming at optimization of the particle size and content of inorganic components, such as O, an organic vehicle, and a viscosity.
[0066]
A plurality of base green sheets 2 to which a copper-based conductive paste for forming the conductive paste body 4 such as the conductive paste film 5 and the conductive paste pillar 6 is applied as described above, and an inorganic material for suppressing shrinkage. The material layer 3 is then laminated, after which, for example, a temperature of 80 ° C. and a pressure of 200 kgf / cm²The raw laminate 1 as shown in FIG. 1 is obtained by pressing in the stacking direction under the above conditions.
[0067]
This raw laminate 1 is then fired in a firing furnace at a temperature at which the low-temperature sintered ceramic material included in the base green sheet 2 is sintered, for example, 900 to 1000 ° C. at the highest temperature, Thereby, the intended multilayer ceramic substrate is obtained.
[0068]
In the firing step described above, the shrinkage-suppressing inorganic material layer 3 itself does not substantially shrink. When the temperature at which the glass is formed in the green sheet for substrate 2 or the temperature at which the glass contained in the green sheet for substrate 2 is softened, the interface between the shrinkage-suppressing inorganic material layer 3 and the green sheet for substrate 2 is reached. In this way, a reaction layer having a thickness of about 2 to 3 μm is formed, and this acts to adhere the shrinkage-inhibiting inorganic material layer 3 and the base green sheet 2 to each other. Accordingly, the inorganic material layer 3 for suppressing shrinkage is in a state of exerting a restraining force for suppressing shrinkage in the main surface direction on the green sheet 2 for the base.
[0069]
For this reason, the green sheet 2 for the substrate is obtained by sintering the low-temperature sintered ceramic material contained therein while substantially suppressing shrinkage in the main surface direction, and substantially shrinking only in the thickness direction. Forming a ceramic layer in the multilayer ceramic substrate formed;
[0070]
In addition, in the inorganic material layer 3 for suppressing shrinkage, a part of the material such as the glass component contained in the green sheet 2 for the base body penetrates, whereby the inorganic material for suppressing shrinkage is fixed, and the inorganic material for suppressing shrinkage. The material layer 3 is solidified.
[0071]
Also, Cu contained in the copper-based conductive paste constituting the conductive paste body 4₂O is reduced to Cu while being contracted, thereby forming a wiring conductor mainly composed of copper. Examples of the wiring conductor include an inner conductor film and an outer conductor film provided by the conductive paste film 5 and a via-hole conductor provided by the conductive paste column 6.
[0072]
  In this firing step, Cu contained in the conductive paste 4₂The time when O reduction occurs is matched with the time when the sintering of the low-temperature sintered ceramic material contained in the base green sheet 2 starts, whereby the contraction behavior of the conductive paste body 4 is changed to the contraction behavior of the base green sheet 2. Is approximated to Therefore, the oxygen partial pressure of the atmosphere in the firing furnace is controlled as follows according to the temperature in the firing furnace.The
[0073]
That is, in the temperature rising process from 200 ° C. to 700 ° C., 10^-6An atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is provided. In this temperature range from 200 ° C. to 700 ° C., 10^-6By using an oxygen partial pressure of mmHg to 10 mmHg, Cu₂O can exist stably. In this temperature range, the low-temperature sintered ceramic material contained in the base green sheet 2 does not start sintering.
[0074]
In this temperature region, the oxygen partial pressure is 10^-6Below mmHg, Cu₂O is reduced to Cu and shrinkage starts in the conductive paste body 4, but shrinkage does not occur in the green sheet 2 for the substrate, which causes warpage and the like in the obtained multilayer ceramic substrate. On the other hand, if the oxygen partial pressure exceeds 10 mmHg, Cu₂Since O is oxidized to CuO and expands, it causes cracks on the ceramic layer side formed by the green sheet 2 for the substrate.
[0075]
Next, in the temperature rising process from 700 ° C. to the shrinkage start temperature of the low-temperature sintered ceramic material, 10^-FourAn atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is provided. In such a temperature range from 700 ° C. to the shrinkage start temperature of the low-temperature sintered ceramic material (for example, 900 ° C.), 10^-FourBy using an oxygen partial pressure of mmHg to 10 mmHg, Cu₂O exists stably. Moreover, since this temperature range is below the shrinkage start temperature of the low-temperature sintered ceramic material, the low-temperature sintered ceramic material contained in the base green sheet 2 is not yet sintered.
[0076]
In this temperature region, the oxygen partial pressure is 10^-FourBelow mmHg, Cu₂O is easily reduced to Cu, causing contraction in the conductive paste body 4 and causing warpage or the like in the obtained multilayer ceramic substrate as in the case of the above-described temperature range. On the other hand, if the oxygen partial pressure exceeds 10 mmHg, Cu₂O is easily oxidized to CuO, and expansion occurs in the conductive paste body 4, which causes cracks as in the case of the temperature region described above.
[0077]
Next, in the temperature raising process from the shrinkage start temperature of the low-temperature sintered ceramic material to 1000 ° C., 10^-3An atmosphere having an oxygen partial pressure of mmHg or less is provided. Under such oxygen partial pressure, Cu₂O is reduced to Cu. In the temperature range from the shrinkage start temperature of the low-temperature sintered ceramic material to 1000 ° C., the low-temperature sintered ceramic material included in the base green sheet 2 is naturally sintered. The sintering of the low-temperature sintered ceramic material causes shrinkage of the green sheet 2 for the substrate or the ceramic layer obtained therefrom, particularly shrinkage in the thickness direction. In the conductive paste 4 or the wiring conductor obtained therefrom, Cu₂Since shrinkage occurs due to reduction from O to Cu, these shrinkage behaviors can be approximated to each other. Therefore, it is possible to prevent the resulting multilayer ceramic substrate from being cracked, warped, raised in relation to the via-hole conductor, and gaps in relation to the via-hole conductor. Can do.
[0078]
In this temperature region, the oxygen partial pressure is 10^-3If it exceeds mmHg, Cu₂O is not reduced to Cu. Therefore, conduction failure in the wiring conductor and warping of the multilayer ceramic substrate occur, and diffusion of Cu ions to the ceramic layer is promoted, causing deterioration of characteristics in the multilayer ceramic substrate.
[0079]
Preferably, the oxygen partial pressure is controlled also in the temperature lowering process. That is, in the temperature lowering process from 1000 ° C. to 200 ° C., 10^-6An atmosphere having an oxygen partial pressure of mmHg or less is provided. As a result, in the outer conductor film formed on the outer surface of the multilayer ceramic substrate, Cu as described above can be used.₂Cu produced by reduction from O is converted into Cu during the cooling process.₂Oxidation to O or CuO is prevented.
[0080]
The control of the oxygen partial pressure as described above can be performed, for example, by mixing an appropriate amount of air in a nitrogen atmosphere. If necessary, H₂O, H₂Ammonia decomposition gas or the like may be used for atmosphere control.
[0081]
Moreover, as a baking furnace for implementing a baking process, a box type batch process type | formula atmosphere furnace can be used, for example, a tubular furnace which can control atmosphere, or a mesh belt type continuous furnace can be used.
[0082]
In addition, for the multilayer ceramic substrate obtained through the above-described firing step, a conductor film may be formed on the outer surface by printing and baking, or plating may be performed on the conductor film, if necessary. A resistor or an insulating layer may be formed, and an appropriate mounting component may be mounted.
[0083]
Firing atmosphere described in the description of the above embodiment, Cu in copper-based conductive paste₂O particle size and Cu in copper-based conductive paste₂An experiment conducted for confirming preferable conditions for the amount of additive other than O will be described below.
[0084]
[Experiment 1]
Experimental Example 1 seeks to obtain preferable conditions for the atmosphere during firing.
[0085]
For low-temperature sintered ceramic materials mixed with powders of barium oxide, silicon oxide, alumina, calcium oxide and boron oxide, polyvinyl butyral as binder, di-n-butyl phthalate as plasticizer, and solvent Toluene and isopropyl alcohol were added and mixed to prepare a slurry. The slurry was formed into a sheet on a carrier film by a doctor blade method and dried to prepare a green sheet for a substrate.
[0086]
Moreover, by adding and mixing polyvinyl butyral as a binder, di-n-butyl phthalate as a plasticizer, toluene and isopropyl alcohol as a solvent, with respect to alumina powder as an inorganic material for shrinkage suppression, A slurry was prepared, and this slurry was applied onto the above-described green sheet for a substrate and dried to form an inorganic material layer for suppressing shrinkage.
[0087]
Further, Cu having an average particle size of 0.5 μm₂10 wt% of an organic vehicle in which ethyl cellulose and terpineol are mixed at a weight ratio of 12:88 is added to 90 wt% of O powder, and the mixture is stirred and kneaded by a stirring crusher and three rolls. A system conductive paste was prepared.
[0088]
Next, through holes are formed in the green sheet for substrate and, if necessary, the inorganic material layer for suppressing shrinkage by a punching machine, and then on the green sheet for substrate or the inorganic material layer for suppressing shrinkage by a screen printing method. The copper-based conductive paste described above was printed to form a conductive paste body such as a conductive paste film and a conductive paste column.
[0089]
Next, a plurality of base green sheets are laminated so as to sandwich the inorganic material layer for suppressing shrinkage, and the temperature is 80 ° C. and the pressure is 200 kgf / cm.²The raw laminate was obtained by pressing in the lamination direction under the above conditions.
[0090]
Next, this raw laminate was fired in a box-type batch processing atmosphere furnace under various oxygen partial pressure conditions as shown in Table 1 to obtain a multilayer ceramic substrate as a sample. This oxygen partial pressure was controlled by mixing air in a nitrogen atmosphere.
[0091]
And about the multilayer ceramic substrate as a sample, while evaluating the presence or absence of a crack and curvature, the state of the conductor film after baking was evaluated. These results are shown in Table 1.
[0092]
The low-temperature sintered ceramic material used in this experiment had a sintering start temperature of 900 ° C.
[0093]
[Table 1]

[0094]
As shown in Table 1, the oxygen partial pressure in the firing process was set in three temperature regions in the temperature raising process, and was also set to a predetermined value in the temperature lowering process. For example, for sample 1, the oxygen partial pressure is set to 20 mmHg in the temperature raising process at 25 to 700 ° C., and is set to 10 mmHg in the temperature raising process at 700 to 900 ° C., and the temperature is raised to 900 to 1000 ° C. In the process, 10^-3It is set to mmHg, and in the temperature lowering process of 1000 to 25 ° C., 10^-6It was set to mmHg.
[0095]
Further, in each column of “crack” and “warp” in Table 1, “◯” indicates that these cracks or warpage did not occur, and “x” indicates that these cracks or warpage occurred. In the column of “conductor film state”, “Cu” indicates that the conductor film is mainly composed of Cu, and “Cu₂O ”means that the conductor film is Cu₂It shows that O is the main component.
[0096]
In the samples shown in Table 1, Samples 2 and 4 to 6 are in a preferable range with respect to the atmospheric conditions during firing. According to these samples 2 and 4 to 6, it was possible to obtain a multilayer ceramic substrate that was free from cracks and warpage and in which Cu was generated in the conductor film.
[0097]
On the other hand, in the sample 1, the oxygen partial pressure in the temperature rising process at 25 to 700 ° C. is 10^-6Since it was too high outside the preferable range of mmHg to 10 mmHg, Cu₂O was oxidized to CuO with volume expansion, and cracks were generated in the obtained multilayer ceramic substrate.
[0098]
In Sample 3, the oxygen partial pressure in the temperature raising process at 700 to 900 ° C. is 10^-FourBefore starting to sinter the low-temperature sintered ceramic material in the green sheet for the substrate because it was too high outside the preferred range of mmHg to 10 mmHg, Cu₂O was oxidized to CuO with volume expansion, and cracks were generated in the obtained multilayer ceramic substrate.
[0099]
In Sample 7, the oxygen partial pressure was 10 in the temperature rising process of 900 to 1000 ° C.^-3Since it was too high outside the preferred range of mmHg or less, Cu₂Sufficient reduction from O to Cu did not occur, so in the conductor film, only the surface was reduced to Cu, but inside the Cu₂O remained. In addition, despite the progress of the sintering of the low-temperature sintered ceramic material in the green sheet for the substrate, Cu₂Since sufficient reduction from O to Cu accompanied by shrinkage does not occur, shrinkage does not occur in the conductive paste body, and thus warpage occurs in the obtained multilayer ceramic substrate.
[0100]
In Sample 8, the oxygen partial pressure was 10 in the temperature lowering process of 1000 to 25 ° C.^-3Since it was set relatively high such as mmHg, Cu was formed on the surface of the conductor film even though Cu was generated in the conductor film at the final stage of the temperature raising process.₂It is thought that it was oxidized to become O and CuO.
[0101]
[Experimental example 2]
Experimental example 2 is Cu in copper-based conductive paste₂In order to obtain a preferable range for the particle size of O. The
[0102]
While carrying out the same operation as in the case of Sample 2 in Table 1, for the copper-based conductive paste, Cu having various average particle diameters as shown in Table 2₂A multilayer ceramic substrate as a sample was obtained using O powder. In Table 2, the average particle diameter is indicated by the value of D50 by a Microtrac particle size distribution meter.
[0103]
In addition, “printability” shown in Table 2 indicates that whether printing by screen printing was successful, whether pasting was easy, and that the conductive paste was embedded in the through hole for the via-hole conductor was good. The “post-firing state” is an evaluation of the state of the wiring conductor obtained by firing the conductive paste, particularly the via-hole conductor.
[0104]
[Table 2]

[0105]
In the samples shown in Table 2, for Samples 12 to 17, Cu₂When the average particle diameter of O is in a preferable range of 0.5 to 10 μm and the content is 50 to 90% by weight, good printability is exhibited and a good wiring conductor is formed after firing. I was able to.
[0106]
On the other hand, in sample 11, Cu₂Since the average particle diameter of O is smaller than 0.5 μm, it is difficult to form a paste even when the content of the organic vehicle is increased to 50% by weight, and a gap is generated in the via-hole conductor after firing.
[0107]
In Sample 18, Cu₂Since the average particle diameter of O is larger than 10 μm, the conductive paste is not sufficiently embedded in the through hole, and a poor conduction occurs in the wiring conductor after firing.
[0108]
[Experiment 3]
Experimental Example 3 is a Cu-based conductive paste Cu₂It is intended to evaluate the effect of improving characteristics by the addition of additives other than O.
[0109]
A ceramic green sheet containing a Ba-Si-Al-B-Ca-O low-temperature sintered ceramic material similar to that in Experimental Example 1 is prepared, and copper-based conductive materials having various compositions shown in Table 3 are prepared thereon. A conductive paste film was formed by applying a conductive paste, and the same atmospheric conditions as in the case of Sample 2 in Table 1 were applied to the firing step to obtain each sample.
[0110]
In this Experimental Example 3, “Cu” shown in Table 3 was used.₂“O” has an average particle diameter of 0.5 μm, “Cu” and “CuO” have an average particle diameter of 2 μm, and “glass” has a softening point of 820 ° C. Barium-based glass frit is used, and “ceramic” is a Ba—Si—Al—B—Ca—O-based ceramic similar to the low-temperature sintered ceramic material contained in the ceramic green sheet described above, and has a sintering temperature of 1000. One having a temperature of ° C. was used, and molybdenum was used as the “metal”.
[0111]
Moreover, about each sample which concerns on these copper-type conductive paste, curvature, conductor film adhesion strength, plating property, solderability, and sheet resistance value were evaluated, respectively.
[0112]
For warping, a conductive paste film is formed with a copper-based conductive paste so that the occupied area is 80% and the film thickness is 15 μm on the surface of a ceramic green sheet that becomes a ceramic plate having a thickness of 4 inches and a thickness of 0.6 mm, and is fired. The absolute value of the warp generated in the later ceramic plate was evaluated. When this warpage is less than 50 μm, it can be evaluated that there is no problem in use.
[0113]
Regarding the conductor film adhesion strength, in order to obtain a sample in which a 2 mm × 2 mm conductor film was formed on a ceramic plate, a ceramic green sheet formed with a conductive paste film was baked. The tensile strength test was carried out in a state where the character lead wires were soldered, and the tensile strength at the time when the conductor film was peeled off is shown. The conductor film adhesion strength is 2 kgf / 2 × 2 mm.²When the value exceeds 1, it can be evaluated that there is no problem in use.
[0114]
Regarding the plating property, nickel plating is performed on a conductor film formed of a copper-based conductive paste as a sample, and the deposition state of this plating film is evaluated.
[0115]
Regarding solder wettability, a conductor film formed using a copper-based conductive paste as a sample is immersed in eutectic solder, and the adhesion state of the solder is evaluated.
[0116]
Regarding the sheet resistance value, a conductive film having a line width of 100 μm and a thickness of 15 μm was formed using a copper-based conductive paste as a sample, and the sheet resistance value was evaluated. When this sheet resistance value is less than 3.0 mΩ / □, it can be evaluated that there is no problem in use.
[0117]
[Table 3]

[0118]
In the sample shown in Table 3, the sample 21 is Cu.₂No additives other than O were added, and for Samples 22 to 34, Cu₂Some additives other than O are added.
[0119]
Among these additives, Cu and CuO are preferably 60% by weight or less, but Samples 31 and 32 exceed the upper limit of 60% by weight. Therefore, the samples 31 and 32 are greatly warped. In particular, the sample 32 is extremely warped, has poor plating properties and solder wettability, and has a sheet resistance value of 3.0 mΩ / □ or more. .
[0120]
Further, the glass, ceramic and metal as additives are preferably contained in an amount of 5% by weight or less. In this regard, for Samples 33 and 34, this upper limit of 5% by weight is exceeded. Therefore, in the sample 33, the plating property and the solder wettability are poor, and the sheet resistance value is as high as 4.5 mΩ /. Sample 34 has a conductor film adhesion strength of 1.8 kgf / 2 × 2 mm.²It is low.
[0121]
【The invention's effect】
As described above, according to the present invention, in a raw laminate that is fired to obtain a multilayer ceramic substrate, a plurality of laminated green sheets for a substrate including a low-temperature sintered ceramic material, and the green for these substrates Cu in relation to a green sheet for a substrate to form a shrinkage-inhibiting inorganic material layer and a wiring conductor disposed along the interface between the sheets and containing the shrinkage-inhibiting inorganic material₂And a conductive paste body formed by applying a copper-based conductive paste containing O. In the step of firing the raw laminate, a green sheet for a substrate is formed by an inorganic material layer for suppressing shrinkage. Cu is contained in the conductive paste body while sintering the low-temperature sintered ceramic material while suppressing shrinkage in the main surface direction of₂Since the wiring conductor is formed by reducing O to Cu, the shrinkage behavior can be approximated between the green sheet for the substrate and the conductive paste body, and cracks and A multilayer ceramic substrate can be produced without any bumps or gaps.
[0122]
Therefore, it is possible to manufacture a multilayer ceramic substrate that is miniaturized and has high wiring density with high reliability.
[0123]
  Also,In this inventionAccording toIn the firing process, in the temperature rising process from 200 ° C. to 700 ° C., Cu₂O is not oxidized to CuO or reduced to Cu 10^-6An atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is given, and in the temperature rising process from 700 ° C. to the shrinkage start temperature of the low-temperature sintered ceramic material,₂O is not oxidized to CuO or reduced to Cu 10^-FourAn atmosphere having an oxygen partial pressure of mmHg to 10 mmHg is given, and in the temperature raising process from the shrinkage start temperature of the low-temperature sintered ceramic material to 1000 ° C., Cu₂O is reduced to Cu 10^-3An atmosphere having an oxygen partial pressure of mmHg or less is provided.BecauseThe shrinkage behavior as described above can be more reliably approximated.
[0124]
In addition, by regulating the oxygen partial pressure as described above, in the temperature region where binder removal occurs, Cu₂Since the oxidizing atmosphere can be given to the extent that O is not oxidized to CuO, it is easy to remove the binder from the green sheet for the substrate and the conductive paste body, the firing time can be shortened, and the obtained multilayer The residue of the carbon component can be reduced in the ceramic substrate. Therefore, a multilayer ceramic substrate having a high density and excellent reliability can be obtained.
[0125]
  UpIn the temperature lowering process from 1000 ° C. to 200 ° C. in the firing step described above, 10^-6When an atmosphere having an oxygen partial pressure of mmHg or less is given, Cu is formed in the temperature lowering process even though Cu is generated in the wiring conductor in the final stage of the temperature raising process.₂Oxidation to O or CuO can be reliably prevented. Therefore, the control of the oxygen partial pressure in such a temperature lowering process exhibits a remarkable effect particularly when a conductive paste film is formed on the outer surface of the raw laminate to be fired.
[0126]
Moreover, the copper-based conductive paste used in the present invention contains 50 to 90% by weight of an organic vehicle, and has an average particle size of 0.5 to 10 μm as a main component of the inorganic component, and a maximum particle size of Cu of 50 μm or less₂If O is included, the conductive paste can be satisfactorily filled into the through-hole for the via-hole conductor, and thus a via-hole conductor without gaps or poor conduction is reliably formed after firing. be able to.
[0127]
In the copper-based conductive paste, Cu, which is the main component of the above-described inorganic component₂Cu and Cu having an average particle diameter of 2 to 10 μm while containing O by 40% by weight or more₂At least one selected from a glass frit or glass bead having a softening point of 800 to 950 ° C., a low-temperature sintered ceramic material, a metal having a melting point of 1100 ° C. or higher, or a metal resinate thereof. By containing 5% by weight or less of the seed additive, the shrinkage behavior during firing of the conductive paste body can be finely adjusted or the conductive paste body can be fired without significantly increasing the resistance value of the wiring conductor. The bonding strength at the interface between the obtained wiring conductor and the ceramic layer obtained by firing the green sheet for the substrate can be improved.
[0128]
Therefore, in designing the multilayer ceramic substrate to be obtained, an electronic circuit can be freely assembled without worrying about the deviation of the distribution density of the wiring conductor. In addition, it is possible to form a wiring conductor excellent in reliability and positional accuracy without deteriorating the high frequency characteristics of the obtained multilayer ceramic substrate and without causing warpage.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a raw laminate 1 produced by a method for producing a multilayer ceramic substrate according to an embodiment of the present invention.
[Explanation of symbols]
1 Raw laminate
2 Green sheet for substrate
3 Inorganic material layer for shrinkage suppression
4 Conductive paste body
5 Conductive paste film
6 Conductive paste pillar

Claims (14)

Preparing a low-temperature sintered ceramic material that can be sintered at a temperature of 1000 ° C. or less;
Preparing an inorganic material for shrinkage suppression that does not sinter at the sintering temperature of the low-temperature sintered ceramic material;
Preparing a copper-based conductive paste containing Cu ₂ O for providing a conductor mainly composed of copper;
A plurality of laminated green sheets for a substrate including the low-temperature sintered ceramic material, and an inorganic material for shrinkage suppression disposed along an interface between the plurality of green sheets for a substrate and including the inorganic material for suppressing shrinkage A step of producing a raw laminate comprising a material layer and a conductive paste formed by applying the copper-based conductive paste in association with the green sheet for a substrate to form a wiring conductor When,
And firing the raw laminate.
In the firing step, the low-temperature sintered ceramic material is sintered while suppressing the shrinkage in the main surface direction of the green sheet for the substrate by the shrinkage-inhibiting inorganic material layer, and included in the conductive paste body The wiring conductor is formed by reducing Cu ₂ O to Cu to be formed ,
In the firing step,
In the temperature rising process from 200 ° C. to 700 ° C. , an atmosphere having an oxygen partial pressure of 10 ⁻⁶ mmHg to 10 mmHg in which Cu ₂ O is not oxidized or reduced to CuO is given.
In the temperature rising process from 700 ° C. to the shrinkage start temperature of the low-temperature sintered ceramic material , an atmosphere having an oxygen partial pressure of 10 ⁻⁴ mmHg to 10 mmHg is given so that Cu ₂ O is not oxidized or reduced to CuO. And
In the temperature rising process from the shrinkage start temperature of the low-temperature sintered ceramic material to 1000 ° C. , an atmosphere having an oxygen partial pressure of 10 ⁻³ mmHg or less in which Cu ₂ O is reduced to Cu is given ,
A method for producing a multilayer ceramic substrate . _2. The multilayer according to claim 1 , wherein in the step of firing, an atmosphere having an oxygen partial pressure of 10 ⁻⁶ mmHg or less in which Cu is not oxidized into Cu ₂ O or CuO is provided in the temperature lowering process from 1000 ° C. to 200 ° C. 3. A method for manufacturing a ceramic substrate. The copper-based conductive paste includes 50 to 90% by weight of an inorganic component and 10 to 50% by weight of an organic vehicle. The main component of the inorganic component has an average particle size of 0.5 to 10 μm, maximum particle size included in the following Cu ₂ O 50 [mu] m, a method for manufacturing a multilayer ceramic substrate according to claim 1 or 2. The inorganic component, Cu comprises ₂ O 40% by weight or more, a method for manufacturing a multilayer ceramic substrate according to claim 3. The said inorganic component is a manufacturing method of the multilayer ceramic substrate of Claim 4 containing 60 weight% or less of at least one of Cu and CuO with an average particle diameter of 2-10 micrometers. The inorganic component includes 5 weights of at least one additive selected from glass frit or glass beads having a softening point of 800 to 950 ° C., the low-temperature sintered ceramic material, and a metal having a melting point of 1100 ° C. or higher or a metal resinate thereof. % Or less, The manufacturing method of the multilayer ceramic substrate of Claim 4 or 5 . The method for producing a multilayer ceramic substrate according to any one of claims 1 to 6 , wherein the low-temperature sintered ceramic material includes a mixture of glass and ceramic. The said low-temperature-sintered ceramic material is a manufacturing method of the multilayer ceramic substrate in any one of Claim 1 thru | or 6 which has the composition which produces | generates glass in the said baking process. The process of producing the said raw laminated body includes the process of forming the conductive paste film for the conductor film extended along the main surface of the said green sheet for base | substrates as the said conductive paste body. A method for producing a multilayer ceramic substrate according to claim 8 . The step of fabricating a laminate of the raw, as the conductive paste material, comprising the step of forming a conductive paste pillars for the via hole conductors extending through the said base green sheets, claims 1 9 The manufacturing method of the multilayer ceramic substrate in any one of. A copper-based conductive paste used for forming a conductive paste column for the via-hole conductor in the method for manufacturing a multilayer ceramic substrate according to claim 10 , comprising 50 to 90% by weight of an inorganic component and 10 to 10%. A copper-based conductive paste comprising 50% by weight of an organic vehicle and containing Cu ₂ O having an average particle size of 0.5 to 10 μm and a maximum particle size of 50 μm or less as a main component of the inorganic component. The copper-based conductive paste according to claim 11 , wherein the inorganic component contains 40% by weight or more of Cu ₂ O. The copper-based conductive paste according to claim 12 , wherein the inorganic component contains 60% by weight or less of at least one of Cu and CuO having an average particle diameter of 2 to 10 µm. The inorganic component includes 5 weights of at least one additive selected from glass frit or glass beads having a softening point of 800 to 950 ° C., the low-temperature sintered ceramic material, and a metal having a melting point of 1100 ° C. or higher or a metal resinate thereof. The copper-based conductive paste according to claim 12 or 13, which comprises not more than%.

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