JP3810206B2 - Wiring board - Google Patents

Wiring board Download PDF

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Publication number
JP3810206B2
JP3810206B2 JP08217898A JP8217898A JP3810206B2 JP 3810206 B2 JP3810206 B2 JP 3810206B2 JP 08217898 A JP08217898 A JP 08217898A JP 8217898 A JP8217898 A JP 8217898A JP 3810206 B2 JP3810206 B2 JP 3810206B2
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metal layer
plating metal
nickel
layer
metallized wiring
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JPH11284298A (en
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雄一 古本
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Kyocera Corp
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Kyocera Corp
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【０００１】
【発明の属する技術分野】
本発明は、半導体素子収納用パッケージや多層配線基板等に用いられる配線基板のメタライズ配線層の被覆構造に関するものである。
【０００２】
【従来の技術】
従来、半導体素子収納用パッケージや多層配線基板等に用いられる配線基板においては、例えば酸化アルミニウム質焼結体等の電気絶縁材料から成る絶縁基体の表面に、半導体素子やチップコンデンサ等の電子部品の電極等を半田付けするためのタングステンやモリブデン・モリブデン−マンガン等の高融点金属から成るメタライズ配線層が被着されている。
【０００３】
そして、このメタライズ配線層の表面には、メタライズ配線層が酸化腐食するのを防止するとともにメタライズ配線層と半田との濡れ性を向上させるために厚みが１〜10μｍ程度のニッケルから成る下地めっき金属層と厚みが0.05〜２μｍ程度の金から成る表面めっき金属層とが順次被着されている。
【０００４】
ところが、ニッケルは金に拡散しやすい性質を有するため、配線基板の製造工程中などにおいて配線基板が加熱されると、この加熱によって下地めっき金属層のニッケルが金から成る表面めっき金属層の表面まで拡散して、表面めっき金属層の耐食性や半田濡れ性を低下させてしまうという問題があった。
【０００５】
そこで、このような配線基板においては、一般にメタライズ配線層の表面に被着された下地めっき金属層をニッケルに２〜60重量％程度のコバルトを含有させて成るニッケル−コバルト合金とし、これにより下地めっき金属層中のニッケルが金から成る表面めっき金属層の表面まで拡散して表面めっき金属層の耐食性や半田濡れ性を低下させるのを防止している。
【０００６】
【発明が解決しようとする課題】
しかしながら、この従来の配線基板によると、表面めっき金属層を構成する金および下地めっき金属層を構成するコバルトを２〜60重量％程度含有するニッケル−コバルト合金が双方とも半田に拡散しやすい性質を有するため、下地めっき金属層および表面めっき金属層が被着されたメタライズ配線層に半導体素子やチップコンデンサ等の電子部品の電極を半田付けすると、表面めっき金属層および下地めっき金属層が殆ど全て半田中に拡散吸収されてしまい、その結果、半田がメタライズ配線層に直接接合することとなって電子部品の電極をメタライズ配線層に強固に半田付けすることができないという欠点を有していた。
【０００７】
本発明は上記欠点を解消すべく案出されたものであり、その目的は、メタライズ配線層に被着させた下地めっき金属層のニッケルが金から成る表面めっき金属層に拡散するのを有効に防止するとともにメタライズ配線層に電子部品の電極等を半田付けした際に下地めっき金属層が半田中に拡散吸収されるのを防止して、メタライズ配線層に電子部品の電極等を強固に半田付けすることができる配線基板を提供することにある。
【０００８】
【課題を解決するための手段】
本発明は、該絶縁基体上に形成されたメタライズ配線層と、コバルトの含有量が１重量％以下のニッケルまたはニッケル−コバルト合金から成り、前記メタライズ配線層の表面に被着された後に熱処理が施された第１の下地めっき金属層と、該第１の下地めっき金属層上に形成され、コバルトの含有量が２〜６０重量％のニッケル−コバルト合金から成る第２の下地めっき金属層と、該第２の下地めっき金属層上に形成され、金を主成分とする表面めっき金属層とを備え、前記第２の下地めっき金属層は、前記第１の下地めっき金属層上に被着された後に、前記熱処理が施されていないを特徴とするものである。
【０００９】
本発明の配線基板によれば、メタライズ配線層の表面にコバルトの含有量が１重量％以下のニッケルまたはニッケル−コバルト合金から成る第１の下地めっき金属層と、コバルトの含有量が２〜60重量％のニッケル−コバルト合金から成る第２の下地めっき金属層と、金を主成分とする表面めっき金属層とを順次被着させたことから、第２の下地めっき金属層により下地めっき金属層のニッケルが金から成る表面めっき金属層に拡散することが有効に防止されるとともに、第１の下地めっき金属層によりメタライズ配線層に電子部品の電極等を半田付けした際に下地めっき金属層の殆ど全てが半田中に拡散吸収されることが防止される。
【００１０】
【発明の実施の形態】
次に本発明を添付図面に基づき詳細に説明する。
図１は本発明の配線基板におけるメタライズ配線層の被覆構造を示す断面図であり、１は酸化アルミニウム質焼結体や窒化アルミニウム質焼結体等の電気絶縁材料から成る絶縁基体、２は絶縁基体１上に形成されたタングステンやモリブデン・モリブデン−マンガン等の高融点金属から成るメタライズ配線層である。
【００１１】
絶縁基体１は、従来周知のセラミックグリーンシート積層法やプレス成形法により生セラミック成形体を形成するとともにこの生セラミック成形体を約1600℃の高温で焼成することによって製作される。
【００１２】
メタライズ配線層２は、例えばタングステンやモリブデンから成る場合であれば、タングステンやモリブデンの粉末に適当な有機バインダや溶剤を添加混合して得た金属ペーストを絶縁基体１となる生セラミック体に従来周知のスクリーン印刷法により所定パターンに印刷しておき、これを絶縁基体１となる生セラミック体とともに焼成することによって形成される。また、モリブデン−マンガンから成る場合であれば、モリブデンおよびマンガンの粉末に適当な有機バインダや溶剤を添加混合して得た金属ペーストを焼成された絶縁基体１の表面に従来周知のスクリーン印刷法により所定パターンに印刷塗布し、これを約1500℃の高温で焼成することによって絶縁基体１の表面に形成される。
【００１３】
メタライズ配線層２は、その表面が、コバルトの含有量が１重量％以下のニッケルまたはニッケル−コバルト合金から成る第１の下地めっき金属層３ａおよびコバルトの含有量が２〜60重量％のニッケル−コバルト合金から成る第２の下地めっき金属層３ｂから成る下地めっき層３と、金を主成分とする表面めっき金属層４とで順次被覆されている。
【００１４】
これらの下地めっき金属層３および表面めっき金属層４は、下地めっき金属層３がメタライズ配線層２に電子部品の電極等を半田付けする際に半田とメタライズ配線層２とを強固に接合するための密着金属として作用し、表面めっき金属層４が下地めっき金属層３の酸化腐食を防止するとともにメタライズ配線層２に電子部品の電極等を半田付けする際に下地めっき金属層３と半田との濡れ性を良好なものとする作用をなす。
【００１５】
下地めっき金属層３を構成する第１の下地めっき金属層３ａは、メタライズ配線層２に電子部品の電極等を半田付けする際に下地めっき金属層３の殆ど全てが半田に拡散吸収されるのを防止する作用をなし、第１の下地めっき金属層３ａに含有されるコバルトが１重量％以下と少ないことから、メタライズ配線層２に電子部品の電極等を半田付けする際に第１の下地めっき金属層３ａが半田に拡散吸収されてしまうことがなく、その結果、第１の下地めっき金属層３ａを介して電子部品の電極等をメタライズ配線層２に強固に半田付けすることが可能となる。
【００１６】
なお、第１の下地めっき金属層３ａは、コバルトの含有量が１重量％を超えると、メタライズ配線層２に電子部品の電極等を半田付けする際に第１の下地めっき金属層３ａが半田に拡散吸収されてしまい易くなり、その結果、第１の下地めっき金属層３ａを介して電子部品の電極等をメタライズ配線層２に強固に接続することが困難となる。従って、第１の下地めっき金属層３ａは、コバルトの含有量が１重量％以下のニッケルまたはニッケルーコバルト合金に特定される。
【００１７】
また、第１の下地めっき金属層３ａは、その厚みが0.5 μｍ未満となると、メタライズ配線層２に電子部品の電極等を半田付けする際に第１の下地めっき金属層３ａを介して電子部品の電極等をメタライズ配線層２に強固に半田付けすることが困難となる傾向にあり、他方、10μｍを超えると第１の下地めっき金属層３ａ中に発生する内部応力が大きなものとなり、この応力により第１の下地めっき金属層３ａがメタライズ配線層２から剥離しやすいものとなる傾向にある。従って、第１の下地めっき金属層３ａは、その厚みを0.5 〜10μｍの範囲としておくことが好ましい。
【００１８】
なお、メタライズ配線層２の表面にコバルトの含有率が１％以下のニッケルまたはニッケル−コバルト合金から成る第１の下地めっき金属層３ａを被着させるには、例えば従来周知のワット浴やスルファミン酸浴に浴中のコバルトイオン濃度が100 ｐｐｍ以下程度となるように硫酸コバルトや塩化コバルトを含有させためっき浴を使用し、電流密度0.5 〜7.0 Ａ／ｄｍ2 でめっきを施す方法が採用され得得る。
【００１９】
そして、第１の下地めっき金属層３ａを被着させた後、これを還元雰囲気中において約600 〜1100℃の温度で熱処理し、第１の下地めっき金属層３ａに内在する応力を緩和するとともにメタライズ配線層２中の高融点金属を第１の下地めっき金属層３ａに、また第１の下地めっき金属層３ａ中のニッケルをメタライズ配線層２に互いに拡散させることによって、第１のめっき金属層３ａがメタライズ配線層２に強固に被着される。
【００２０】
また、第１の下地めっき金属層３ａ上に被着された第２の下地めっき金属層３ｂは、下地めっき金属層３のニッケルが表面めっき金属層４の表面まで拡散して表面めっき金属層４の耐食性や半田濡れ性が低下するのを防止する作用をなし、第２の下地めっき金属層３ｂに含有されるコバルトが２〜60重量％と多いことから、配線基板の製造工程等において配線基板が加熱されても、この加熱によって下地めっき金属層３のニッケルが表面めっき金属層４の表面まで拡散することが有効に防止され、その結果、表面めっき金属層４の耐食性や半田濡れ性が低下してしまうようなことはない。
【００２１】
なお、第２の下地めっき金属層３ｂは、これに含有されるコバルトが２重量％未満では、配線基板の製造工程等において配線基板が加熱された場合、下地めっき金属層３のニッケルが表面めっき金属層４の表面まで拡散することを有効に防止することができなくなる傾向にあり、また60重量％を超えるとメタライズ配線層２に電子部品の電極等を半田付けする際に半田付け性が悪いものとなる傾向にある。従って、第２の下地めっき金属層３ｂは、コバルトの含有量が２〜60重量％の範囲のニッケル−コバルト合金に特定される。
【００２２】
また、第２の下地めっき金属層３ｂは、その厚みが0.5 μｍ未満となると、配線基板の製造工程等において配線基板が加熱された際にその加熱によって下地めっき金属層３のニッケルが表面めっき金属層４の表面にまで拡散してしまいやすいものとなり、他方、10μｍを超えると第２の下地めっき金属層３ｂ中に発生する内部応力が大きなものとなり、この応力により第２の下地めっき金属層３ｂがメタライズ配線層２から剥離しやすいものとなる傾向にある。従って、第２の下地めっき金属層３ｂは、その厚みを0.5 〜10μｍの範囲としておくことが好ましい。
【００２３】
なお、メタライズ配線層２の表面に第１の下地めっき金属層３ａを被着させるには、例えば従来周知のワット浴やスルファミン酸浴に浴中のコバルトイオン濃度が500 〜20000 ｐｐｍ程度となるように硫酸コバルトや塩化コバルトを含有させためっき浴を使用し0.5 〜７Ａ／ｄｍ2 の電流密度でめっきを施す方法が採用され得る。
【００２４】
そして、第２の下地めっき金属層３ｂを被着させた後、これを還元雰囲気中において約600 〜1100℃の温度で熱処理してもよいが、この熱処理により第２の下地めっき金属層３ｂに含有されるコバルトが第１の下地めっき金属層３ａに大量に拡散して、第１の下地めっき金属層３ａの有する半田への拡散防止作用を阻害してしまう危険性がある。従って、第２の下地めっき金属層３ｂを被着させた後は、熱処理をしない方が好ましい。
【００２５】
また、下地めっき金属層３の上に被着される金を主成分とする表面めっき金属層４は、下地めっき金属層３が酸化腐食するのを防止するとともに下地めっき金属層３と半田との濡れ性を向上させる作用をなすが、その厚みが0.05μｍ未満では下地めっき金属層３が酸化腐食するのを有効に防止することができなくなる傾向にあり、他方、２μｍを超えると、メタライズ配線層２に電子部品の電極等を半田付けする際に表面めっき金属層４中の金が半田中に大量に拡散してこれが半田中の錫との間で脆弱な金−錫合金を多量に作り、その結果、電子部品の電極等をメタライズ配線層２に強固に半田付けすることができなくなる傾向にある。従って表面めっき金属層４は、その厚みを0.05〜２μｍの範囲としておくことが好ましく、さらに好適には0.1 〜0.5 μｍの範囲としておくことが好ましい。
【００２６】
なお、金を主成分とする表面めっき金属層４は、例えば従来周知の中性シアン化金めっき浴を使用し、0.1 〜1.0 Ａ／ｄｍ2 の電流密度でめっきを施す方法が採用され得る。
【００２７】
かくして本発明によれば、メタライズ配線層に被着されためっき金属層が耐食性および半田濡れ性に優れ、かつメタライズ配線層への強固な半田付けが可能な配線基板を提供することができる。
【００２８】
【発明の効果】
本発明の配線基板によれば、メタライズ配線層の表面にコバルトの含有量が１重量％以下のニッケルまたはニッケル−コバルト合金から成る第１の下地めっき金属層と、コバルトの含有量が２〜60重量％のニッケル−コバルト合金から成る第２の下地めっき金属層と、金を主成分とする表面めっき金属層とを順次被着させたことから、第２の下地めっき金属層により下地めっき金属層のニッケルが金から成る表面めっき金属層に拡散することが有効に防止され、表面めっき金属層の耐食性および半田濡れ性が低下することがなくなるとともに、第１の下地めっき金属層によりメタライズ配線層に電子部品の電極等を半田付けした際に下地めっき金属層の殆ど全てが半田中に拡散吸収されることが防止され、メタライズ配線層に電子部品の電極等を強固に半田付けすることができる。
【図面の簡単な説明】
【図１】本発明の配線基板におけるメタライズ配線層の被覆構造を示す断面図である。
【符号の説明】
１・・・・・・絶縁基体
２・・・・・・メタライズ配線層
３・・・・・・下地めっき金属層
３ａ・・・・第１の下地めっき金属層
３ｂ・・・・第２の下地めっき金属層
４・・・・・・表面めっき金属層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating structure of a metallized wiring layer of a wiring board used for a package for housing a semiconductor element, a multilayer wiring board or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a wiring board used for a semiconductor element storage package or a multilayer wiring board, an electronic component such as a semiconductor element or a chip capacitor is formed on the surface of an insulating base made of an electrically insulating material such as an aluminum oxide sintered body. A metallized wiring layer made of a refractory metal such as tungsten or molybdenum / molybdenum-manganese is used to solder electrodes and the like.
[0003]
On the surface of the metallized wiring layer, an underlying plating metal made of nickel having a thickness of about 1 to 10 μm is used to prevent the metallized wiring layer from being oxidized and corroded and to improve the wettability between the metallized wiring layer and the solder. A layer and a surface plating metal layer made of gold having a thickness of about 0.05 to 2 μm are sequentially deposited.
[0004]
However, since nickel has the property of easily diffusing into gold, when the wiring board is heated during the manufacturing process of the wiring board, the nickel of the base plating metal layer is heated to the surface of the surface plating metal layer made of gold. There is a problem in that it diffuses to lower the corrosion resistance and solder wettability of the surface plated metal layer.
[0005]
Therefore, in such a wiring board, generally, the base plating metal layer deposited on the surface of the metallized wiring layer is a nickel-cobalt alloy in which about 2 to 60% by weight of cobalt is contained in nickel. The nickel in the plating metal layer is prevented from diffusing up to the surface of the surface plating metal layer made of gold, thereby reducing the corrosion resistance and solder wettability of the surface plating metal layer.
[0006]
[Problems to be solved by the invention]
However, according to this conventional wiring board, the nickel-cobalt alloy containing about 2 to 60% by weight of the gold constituting the surface plating metal layer and the cobalt constituting the base plating metal layer tends to diffuse into the solder. Therefore, when the electrodes of electronic components such as semiconductor elements and chip capacitors are soldered to the metallized wiring layer coated with the base plating metal layer and the surface plating metal layer, almost all of the surface plating metal layer and the base plating metal layer are soldered. As a result, the solder is directly bonded to the metallized wiring layer, so that the electrodes of the electronic component cannot be firmly soldered to the metallized wiring layer.
[0007]
The present invention has been devised to eliminate the above-mentioned drawbacks, and its purpose is to effectively diffuse the nickel of the base plating metal layer deposited on the metallized wiring layer into the surface plating metal layer made of gold. In addition to preventing the metal plating layer from being diffused and absorbed into the solder when the electronic component electrodes are soldered to the metallized wiring layer, the electronic component electrodes are firmly soldered to the metallized wiring layer. An object of the present invention is to provide a wiring board that can be used.
[0008]
[Means for Solving the Problems]
The present invention comprises a metallized wiring layer formed on the insulating substrate and nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less, and is heat-treated after being deposited on the surface of the metallized wiring layer. A first undercoating metal layer applied, and a second undercoating metal layer formed on the first undercoating metal layer and made of a nickel-cobalt alloy having a cobalt content of 2 to 60% by weight; And a surface plating metal layer mainly composed of gold, which is formed on the second under plating metal layer, and the second under plating metal layer is deposited on the first under plating metal layer. After the heat treatment, the heat treatment is not performed.
[0009]
According to the wiring board of the present invention, the surface of the metallized wiring layer has a first undercoating metal layer made of nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less, and a cobalt content of 2 to 60. Since the second undercoating metal layer made of nickel-cobalt alloy of weight% and the surface plating metal layer mainly composed of gold were sequentially deposited, the undercoating metal layer was formed by the second undercoating metal layer. The nickel is effectively prevented from diffusing into the surface plating metal layer made of gold, and when the electrodes of the electronic component are soldered to the metallized wiring layer by the first base plating metal layer, Almost all is prevented from being diffused and absorbed in the solder.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a coating structure of a metallized wiring layer in a wiring board of the present invention, wherein 1 is an insulating substrate made of an electrically insulating material such as an aluminum oxide sintered body or an aluminum nitride sintered body, and 2 is an insulating substrate. This is a metallized wiring layer made of a refractory metal such as tungsten or molybdenum / molybdenum-manganese formed on the substrate 1.
[0011]
The insulating substrate 1 is manufactured by forming a green ceramic molded body by a conventionally known ceramic green sheet lamination method or press molding method and firing the green ceramic molded body at a high temperature of about 1600 ° C.
[0012]
If the metallized wiring layer 2 is made of, for example, tungsten or molybdenum, a metal paste obtained by adding and mixing an appropriate organic binder or solvent to tungsten or molybdenum powder is conventionally known as a raw ceramic body serving as the insulating substrate 1. It is formed by printing a predetermined pattern by the screen printing method and firing it together with the green ceramic body to be the insulating substrate 1. In the case of molybdenum-manganese, a metal paste obtained by adding and mixing an appropriate organic binder and solvent to the molybdenum and manganese powder is applied to the surface of the baked insulating substrate 1 by a conventionally known screen printing method. It is formed on the surface of the insulating substrate 1 by printing and coating a predetermined pattern and baking it at a high temperature of about 1500 ° C.
[0013]
The metallized wiring layer 2 has a first base plating metal layer 3a made of nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less and a nickel content having a cobalt content of 2 to 60% by weight. A base plating layer 3 made of a second base plating metal layer 3b made of a cobalt alloy and a surface plating metal layer 4 mainly composed of gold are sequentially coated.
[0014]
The base plating metal layer 3 and the surface plating metal layer 4 are used to firmly bond the solder and the metallized wiring layer 2 when the base plating metal layer 3 solders the electrodes of the electronic component to the metallized wiring layer 2. The surface plating metal layer 4 prevents oxidative corrosion of the base plating metal layer 3 and the solder of the base plating metal layer 3 and the solder when soldering the electrodes of the electronic component to the metallized wiring layer 2. It acts to improve the wettability.
[0015]
The first undercoating metal layer 3a constituting the undercoating metal layer 3 is such that almost all of the undercoating metal layer 3 is diffused and absorbed by the solder when the electrodes of the electronic components are soldered to the metallized wiring layer 2. Since the cobalt contained in the first base plating metal layer 3a is as low as 1% by weight or less, the first base layer is soldered to the metallized wiring layer 2 when soldering an electrode of an electronic component or the like. The plated metal layer 3a is not diffused and absorbed by the solder, and as a result, it is possible to firmly solder the electrodes and the like of the electronic component to the metallized wiring layer 2 via the first base plated metal layer 3a. Become.
[0016]
When the content of cobalt exceeds 1% by weight, the first base plating metal layer 3a is soldered when the electrodes of the electronic components are soldered to the metallized wiring layer 2. As a result, it becomes difficult to firmly connect the electrodes of the electronic component and the like to the metallized wiring layer 2 via the first base plating metal layer 3a. Accordingly, the first undercoat metal layer 3a is specified as nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less.
[0017]
Further, when the thickness of the first base plating metal layer 3a is less than 0.5 μm, the electronic component is interposed via the first base plating metal layer 3a when soldering the electrode of the electronic component to the metallized wiring layer 2 or the like. However, when the thickness exceeds 10 μm, the internal stress generated in the first undercoat metal layer 3a becomes large, and this stress Therefore, the first base plating metal layer 3a tends to be easily separated from the metallized wiring layer 2. Therefore, the thickness of the first base plating metal layer 3a is preferably in the range of 0.5 to 10 μm.
[0018]
In order to deposit the first base plating metal layer 3a made of nickel or nickel-cobalt alloy having a cobalt content of 1% or less on the surface of the metallized wiring layer 2, for example, a conventionally known Watt bath or sulfamic acid is used. A method can be employed in which a plating bath containing cobalt sulfate or cobalt chloride is used so that the cobalt ion concentration in the bath is about 100 ppm or less and plating is performed at a current density of 0.5 to 7.0 A / dm 2. obtain.
[0019]
Then, after the first undercoat metal layer 3a is deposited, it is heat-treated at a temperature of about 600 to 1100 ° C. in a reducing atmosphere to relieve the stress inherent in the first undercoat metal layer 3a. By diffusing the refractory metal in the metallized wiring layer 2 into the first base plating metal layer 3a and the nickel in the first base plating metal layer 3a into the metallized wiring layer 2, the first plating metal layer 3 a is firmly attached to the metallized wiring layer 2.
[0020]
Further, the second undercoat metal layer 3b deposited on the first undercoat metal layer 3a has a surface plated metal layer 4 in which nickel of the undercoat metal layer 3 diffuses to the surface of the surface plated metal layer 4. This prevents the deterioration of the corrosion resistance and solder wettability, and the cobalt contained in the second base plating metal layer 3b is as high as 2 to 60% by weight. Even when the surface is heated, the nickel of the base plating metal layer 3 is effectively prevented from diffusing up to the surface of the surface plating metal layer 4, and as a result, the corrosion resistance and solder wettability of the surface plating metal layer 4 are reduced. There is no such thing as doing it.
[0021]
The second base plating metal layer 3b is such that the cobalt contained therein is less than 2% by weight, and the nickel of the base plating metal layer 3 is surface plated when the wiring substrate is heated in the manufacturing process of the wiring substrate. It tends to be impossible to effectively prevent diffusion to the surface of the metal layer 4, and when it exceeds 60% by weight, the solderability is poor when soldering the electrodes of the electronic component to the metallized wiring layer 2. It tends to be a thing. Therefore, the second undercoat metal layer 3b is specified as a nickel-cobalt alloy having a cobalt content in the range of 2 to 60% by weight.
[0022]
Further, when the thickness of the second base plating metal layer 3b is less than 0.5 μm, when the wiring board is heated in the manufacturing process of the wiring board, the nickel of the base plating metal layer 3 is heated by the surface plating metal. On the other hand, if it exceeds 10 μm, the internal stress generated in the second undercoat metal layer 3b becomes large, and this stress causes the second undercoat metal layer 3b to be diffused. Tends to be easily peeled off from the metallized wiring layer 2. Therefore, it is preferable that the thickness of the second base plating metal layer 3b be in the range of 0.5 to 10 μm.
[0023]
In order to deposit the first undercoat metal layer 3a on the surface of the metallized wiring layer 2, the cobalt ion concentration in the bath is, for example, about 500 to 20000 ppm in a conventionally known watt bath or sulfamic acid bath. Alternatively, a plating bath containing cobalt sulfate or cobalt chloride may be used and plating may be performed at a current density of 0.5 to 7 A / dm 2 .
[0024]
Then, after the second undercoat metal layer 3b is deposited, it may be heat-treated at a temperature of about 600 to 1100 ° C. in a reducing atmosphere. By this heat treatment, the second undercoat metal layer 3b is formed. There is a risk that the contained cobalt diffuses in a large amount in the first base plating metal layer 3a and inhibits the diffusion preventing action to the solder of the first base plating metal layer 3a. Therefore, it is preferable not to perform heat treatment after the second base plating metal layer 3b is deposited.
[0025]
Further, the surface plating metal layer 4 mainly composed of gold deposited on the base plating metal layer 3 prevents the base plating metal layer 3 from being oxidized and corroded. Although it improves the wettability, if the thickness is less than 0.05 μm, it tends to be impossible to effectively prevent the underlying plating metal layer 3 from being oxidatively corroded. On the other hand, if the thickness exceeds 2 μm, the metallized wiring layer When the electrodes of the electronic parts are soldered to 2, gold in the surface plating metal layer 4 diffuses in a large amount in the solder, and this creates a large amount of fragile gold-tin alloy with the tin in the solder, As a result, there is a tendency that the electrodes of the electronic component cannot be firmly soldered to the metallized wiring layer 2. Therefore, the surface plating metal layer 4 preferably has a thickness in the range of 0.05 to 2 μm, and more preferably in the range of 0.1 to 0.5 μm.
[0026]
In addition, the surface plating metal layer 4 which has gold as a main component can employ | adopt the method of plating with the current density of 0.1-1.0 A / dm < 2 >, for example using a conventionally well-known neutral gold cyanide plating bath.
[0027]
Thus, according to the present invention, it is possible to provide a wiring board in which the plated metal layer deposited on the metallized wiring layer is excellent in corrosion resistance and solder wettability and can be firmly soldered to the metallized wiring layer.
[0028]
【The invention's effect】
According to the wiring board of the present invention, the surface of the metallized wiring layer has a first undercoating metal layer made of nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less, and a cobalt content of 2 to 60. Since the second undercoating metal layer made of nickel-cobalt alloy of weight% and the surface plating metal layer mainly composed of gold were sequentially deposited, the undercoating metal layer was formed by the second undercoating metal layer. The nickel is effectively prevented from diffusing into the surface plating metal layer made of gold, and the corrosion resistance and solder wettability of the surface plating metal layer are not lowered. When the electrodes of electronic parts are soldered, almost all of the underlying plating metal layer is prevented from being diffused and absorbed in the solder, and the electrodes of the electronic parts are prevented from being metallized wiring layers. It is possible to firmly soldered.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a covering structure of a metallized wiring layer in a wiring board of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Insulating base | substrate 2 ... Metallized wiring layer 3 ... Base metal layer 3a ... First base metal layer 3b ... Second Underlying metal layer 4 ··· Surface plating metal layer

Claims (2)

絶縁基体と、
該絶縁基体上に形成されたメタライズ配線層と、
コバルトの含有量が１重量％以下のニッケルまたはニッケル−コバルト合金から成り、前記メタライズ配線層の表面に被着された後に熱処理が施された第１の下地めっき金属層と、
該第１の下地めっき金属層上に形成され、コバルトの含有量が２〜６０重量％のニッケル−コバルト合金から成る第２の下地めっき金属層と、
該第２の下地めっき金属層上に形成され、金を主成分とする表面めっき金属層とを備え、
前記第２の下地めっき金属層は、前記第１の下地めっき金属層上に被着された後に、前記熱処理が施されていないことを特徴とする配線基板。An insulating substrate;
A metallized wiring layer formed on the insulating substrate;
A first base plating metal layer made of nickel or a nickel-cobalt alloy having a cobalt content of 1% by weight or less, applied to the surface of the metallized wiring layer, and then subjected to a heat treatment;
A second undercoating metal layer formed on the first undercoating metal layer and made of a nickel-cobalt alloy having a cobalt content of 2 to 60% by weight;
A surface plating metal layer mainly composed of gold formed on the second base plating metal layer ,
The wiring board according to claim 1, wherein the second base plating metal layer is not subjected to the heat treatment after being deposited on the first base plating metal layer . 前記第１の下地めっき金属層は、６００〜１１００℃の前記熱処理が施されていることを特徴とする請求項１記載の配線基板。  The wiring board according to claim 1, wherein the heat treatment at 600 to 1100 ° C. is performed on the first base plating metal layer.
JP08217898A 1998-03-27 1998-03-27 Wiring board Expired - Fee Related JP3810206B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP08217898A JP3810206B2 (en) 1998-03-27 1998-03-27 Wiring board

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP08217898A JP3810206B2 (en) 1998-03-27 1998-03-27 Wiring board

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Publication Number Publication Date
JPH11284298A JPH11284298A (en) 1999-10-15
JP3810206B2 true JP3810206B2 (en) 2006-08-16

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Family Applications (1)

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