JP3751805B2 - Method for forming metal thin film - Google Patents

Description

表１から明らかなように、比較例１に比べて、ステンレス基板の表面に合成樹脂を付着させた実施例１〜８は、密着力ｂが向上していることがわかる。また、密着力ａも良好であることがわかる。また、官能基比率Ｒが４１である実施例７は、他の実施例１〜６、８に比べると、密着力が少し低下していることがわかる。
【００７９】
【発明の効果】
以上述べたように、本発明の金属薄膜の形成方法によれば、真空蒸着によって、金属の表面と絶縁層の表面との両方に、十分に密着性を向上させながら金属薄膜を形成することができ、このような、本発明の金属薄膜の形成方法を用いて、配線回路基板用基材、配線回路基板および回路付サスペンション基板を製造すれば、信頼性が高く良好な品質を有するものを得ることができる。
【図面の簡単な説明】
【図１】 本発明のプラズマ処理および真空蒸着を行なうための処理装置の一実施形態を示す概略説明図である。
【図２】 回路付サスペンション基板の製造工程の一例を示す工程図であって、
（ａ）は、サスペンション基板である金属基板を示す断面図、
（ｂ）は、金属基板上に、ベース層を所定のパターンとして形成する工程を示す断面図、
（ｃ）は、ベース層が形成されていない金属基板の表面に、絶縁層の形成に用いられる合成樹脂を付着させる工程を示す断面図、
（ｄ）は、真空蒸着によって、蒸着クロム層および蒸着銅層を順次形成する工程を示す断面図を示す。
【図３】 図２に続いて、回路付サスペンション基板の製造工程の一例を示す工程図であって、
（ｅ）は、金属薄膜上に、所定のレジストパターンでめっきレジストを形成する工程を示す断面図、
（ｆ）は、めっきレジストが形成されていない部分に、電解めっきにより、所定の配線パターンの導体層を形成する工程を示す断面図、
（ｇ）は、めっきレジストおよびそのめっきレジストが形成されていた金属薄膜を、化学エッチングにより除去する工程を示す断面図、
（ｈ）は、導体層を被覆するポリイミドなどからなるカバー層を、公知の方法によって形成する工程を示す断面図である。
【図４】 図２（ｃ）において、ベース層が形成されていない金属基板の表面に、絶縁層の形成に用いられる合成樹脂を付着させる工程を説明するための工程図であって、
（ａ）は、金属基板の全面に、感光性樹脂の皮膜を形成する工程を示す断面図、
（ｂ）は、フォトマスクを介して露光する工程を示す断面図、
（ｃ）は、現像する工程を示す断面図である。
【図５】 図４に続いて、図２（ｃ）において、ベース層が形成されていない金属基板の表面に、絶縁層の形成に用いられる合成樹脂を付着させる工程を説明するための工程図であって、
（ｄ）は、所定のパターンの皮膜が形成された金属基板を、真空容器内に設置して減圧する工程を示す断面図、
（ｅ）は、皮膜から、その皮膜を形成する感光性樹脂の分子を飛散させて、金属基板の表面に付着させ、皮膜および合成樹脂を硬化させる工程を示す断面図である。
【図６】 密着力の測定に用いるサンプルを説明するための説明図である。
【符号の説明】
３１ 金属基板
３２ ベース層
３３ 合成樹脂
３７ 金属薄膜[0001]
BACKGROUND OF THE INVENTION
  The present invention provides a method for forming a metal thin film.To the lawRelated.
[0002]
[Prior art]
Conventionally, in a method for manufacturing a wired circuit board such as a SUS method or a suspension board with circuit, for example, an insulating layer made of polyimide or the like is laminated on a metal substrate made of a SUS board or the like, and the insulating layer is formed. After forming into a predetermined pattern, a metal thin film made of chromium, copper or the like is vacuum-deposited on the insulating layer, and then the conductor layer made of copper or the like is formed into a predetermined pattern by plating using the metal thin film as a seed film. A method of forming has been implemented.
[0003]
[Problems to be solved by the invention]
However, in the above method for manufacturing a printed circuit board, the metal thin film is formed by vacuum deposition on the metal substrate on which the insulating layer is formed in a predetermined pattern. It is simultaneously formed on the surface of the substrate under the same vapor deposition conditions.
[0004]
On the other hand, in general, when a metal thin film is formed on a predetermined adherend by vacuum vapor deposition, the adherend is preliminarily plasma-treated in order to improve the adhesion between the metal thin film and the adherend. Appropriate plasma conditions are selected according to the properties of the adherend. For example, when the adherend is a metal material, the treatment with oxygen plasma improves the adhesion of the metal thin film. When the adherend is an organic material, the treatment with nitrogen plasma results in a metal The adhesion of the thin film is improved.
[0005]
However, in such plasma treatment, the plasma conditions differ greatly between the case where the adherend is a metal material and the case where it is an organic material, and both the surface of the metal material and the surface of the organic material are different. It is difficult to improve the adhesion at the same time. Therefore, in the above-described method for manufacturing a printed circuit board, in forming a metal thin film by vacuum evaporation, the adhesion between the metal substrate and the insulating layer formed on the metal substrate is improved with respect to the metal thin film. It is difficult.
[0006]
  The present invention has been made in view of such circumstances. The object of the present invention is to form a metal thin film while sufficiently improving the adhesion to both the metal surface and the insulating layer surface by vacuum deposition. How to form a metal thin film that can be formedThe lawIt is to provide.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides:The insulating layer is formed as a predetermined pattern on the metal substrate, the base material having the surface of the metal and the surface of the insulating layer, or the metal is formed as the predetermined pattern on the insulating layer,A method of forming a metal thin film by vacuum vapor deposition on a substrate having a metal surface and an insulating layer surface, and before the vacuum vapor deposition,, Synthetic resin used to form insulating layersAttach, Plasma treatment of the surfaceIt is characterized by that.
[0008]
  In this method, the aboveSynthetic resin used to form insulating layersIt is preferable to plasma-treat the surface ofSynthetic resin used to form insulating layersThe functional group ratio R represented by the following formula (1) on the surface is preferably 47 or more.
[0009]
                    R = (b + c) / a (1)
(In the above formula (1), a, b, and c represent the spectral intensity of C1s measured by ESCA, a is based on CHn (n is an integer of 0 to 3), and b is C—O and C—N. Based on, c indicates based on COO. )
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The method for forming a metal thin film of the present invention is applied to a substrate having a metal surface and an insulating layer surface. Examples of such a base material include a base material in which an insulating layer is formed as a predetermined pattern on a metal substrate.
[0011]
Examples of the metal substrate include a metal foil or a metal thin plate such as stainless steel (SUS), copper, aluminum, iron, nickel, and 42 alloy. Moreover, the thickness is about 10-100 micrometers, for example.
[0012]
As the insulating layer, an organic material is used, and examples thereof include synthetic resins such as polyimide, polyamide, polyethylene terephthalate, polyester, polyethersulfone, polysulfone, acrylic, polyethernitrile, polyethylene naphthalate, and polyvinyl chloride.
[0013]
In order to form the insulating layer as a predetermined pattern on the metal substrate, for example, by applying the above-mentioned synthetic resin solution on the metal substrate, drying, and etching using a photoresist or the like, A predetermined pattern may be formed, or the above-described synthetic resin dry film may be attached to a metal substrate and then etched using a photoresist or the like to be processed into a predetermined pattern.
[0014]
Moreover, if a photosensitive resin is used as the synthetic resin, the insulating layer can be efficiently and reliably formed as a predetermined pattern on the metal substrate. That is, when using a photosensitive resin, first, a solution of the photosensitive resin is coated on the entire surface of the support substrate, dried to form a film, and then exposed through a photomask. The exposed portion is heated to a predetermined temperature by developing with a positive type or a negative type, thereby forming the formed film into a predetermined pattern, and then forming the photosensitive resin film into the predetermined pattern. By heating and curing, the insulating layer can be formed as a predetermined pattern on the metal substrate. As such a photosensitive resin, for example, a photosensitive polyimide such as polyamic acid is preferably used.
[0015]
Thus, the pattern shape of the insulating layer formed on the metal substrate is not limited at all, and the thickness thereof is, for example, about 5 to 30 μm.
[0016]
In addition, a base material having a metal surface and an insulating layer surface to which the method for forming a metal thin film of the present invention is applied is such that the insulating layer is formed as a predetermined pattern on the metal substrate. In addition to the material, for example, on the contrary, a base material in which a metal is formed in a predetermined pattern on the insulating layer may be used. As the insulating layer and metal of such a substrate, the same insulating layer and metal as described above can be used.
[0017]
  And in the formation method of the metal thin film of this invention, before forming a metal thin film by vacuum deposition with respect to such a base material, it is previously applied to the metal surface., Synthetic resin used to form insulating layersKeep it attached. That is, in the base material in which the insulating layer is formed as a predetermined pattern on the metal substrate, the metal surface of the metal substrate is, Synthetic resin used to form insulating layersKeep it attached.
[0018]
  On metal surface, Synthetic resin used to form insulating layersThere is no particular limitation on the method of attaching the metal to the surface of the metal., Synthetic resin used to form insulating layersCan be used, any known method can be used. Also,Synthetic resin used to form insulating layersWhen adhering to the metal surface,Synthetic resin used to form insulating layersIt is preferable that the insulating layer is deposited in a partially dotted manner. Examples of such a method include a PVD method (physical vapor deposition method) and a plasma polymerization method. For example, a method of partially leaving the surface.
[0019]
  In the PVD method, for example, using a vacuum vessel, in the vacuum vessel,Synthetic resin used to form insulating layersThe target can be deposited on the metal surface of the metal substrate by setting the target and the metal substrate, and sputtering or heating the target in a vacuum vessel..
[0020]
Note that an insulating layer formed over a metal substrate may be used as a target as it is. If the insulating layer is used as it is as a target, it is not necessary to prepare a target separately, and efficient vapor deposition can be performed. In particular, when a photosensitive resin is used for forming the insulating layer, by using a photosensitive resin film in a predetermined pattern before curing as a target, simple and reliable vapor deposition can be performed as described later. it can.
[0021]
  Moreover, the vapor deposition conditions of the PVD method are the type of target and the type of adhesion.Synthetic resinHowever, the temperature is 200 to 450 ° C., preferably 250 to 400 ° C., and the atmospheric pressure (degree of vacuum) is 10.^-1-10^ThreePa, preferably 1-10²Pa and the treatment time is 0.1 to 10 hours, preferably 1 to 5 hours. In these vapor deposition conditions, it adheres by changing the atmospheric pressure (degree of vacuum) in particular.Synthetic resinThe thickness of can be adjusted.
[0022]
Further, in the plasma polymerization method, for example, a resin formed by using a vacuum vessel, placing a metal substrate in the vacuum vessel, introducing an organic monomer under a plasma atmosphere, and polymerizing the organic monomer. Is adsorbed on the surface of the metal.
[0023]
Such plasma polymerization may be performed under known polymerization conditions, and examples of the organic monomer include organic monomers of synthetic resins used for forming the insulating layer described above.
[0024]
  In these PVD methods and plasma polymerization methods, not only on the metal surface but also on the surface of the insulating layer.Synthetic resinIs attached.
[0025]
Furthermore, in the method of leaving the insulating layer partially on the metal surface during the etching of the insulating layer, for example, the insulating layer remains on the surface of the metal substrate where the insulating layer pattern is not originally formed. The etching conditions are appropriately selected depending on the type of the insulating layer, the shape of the pattern, and the like.
[0026]
  In this way it adheres to the metal surface, Synthetic resin used to form insulating layersAre attached in such a manner that they are partially scattered on the surface of the metal, and the degree of distribution thereof is, for example, about 2 to 50%, preferably 4 to 20 per unit area of the surface of the metal. %. Further, the shape is approximately circular, the diameter is approximately 20 to 80 nm, and the thickness is approximately 2 to 30 nm, preferably approximately 2 to 10 nm. If it is too thin, there will be no effect of improving the adhesion, and if it is too thick, the substrate may be warped in the subsequent process, or it may become a foreign substance during etching of the metal substrate, leading to a reduction in quality.
[0027]
  Also, in a multilayer wiring board or the like, when it is necessary to form a conductor layer pattern not only on the insulating layer but also on the metal substrate, good electrical conductivity is required between the metal substrate and the conductor layer. In that case,Synthetic resinIf the thickness is too thick, the continuity may be poor.
[0028]
  In the metal thin film forming method of the present invention, the metal surface is thus formed., Synthetic resin used to form insulating layersA metal thin film is formed by vacuum deposition on the substrate to which is attached, but before the vacuum deposition,Synthetic resinIncluding its surfaceSynthetic resinIt is preferable to plasma-treat the surface of the metal to which is attached and the surface of the insulating layer. By performing the plasma treatment, the adhesion of the metal thin film to the substrate can be improved.
[0029]
For the plasma treatment, for example, a vacuum vessel may be used, and a metal substrate may be disposed in the vacuum vessel, and an atmospheric gas may be enclosed and discharged. As a condition for the plasma treatment, a condition of nitrogen plasma for treating an organic material is preferable. That is, as the atmospheric gas, for example, nitrogen, oxygen, argon, or the like can be used, but preferably nitrogen or a mixed gas containing nitrogen is used.
[0030]
  In such plasma treatment,Synthetic resinIs preferably modified so that the functional group ratio R represented by the following formula (1) is 47 or more.
[0031]
                    R = (b + c) / a (1)
(In the above formula (1), a, b, and c represent the spectral intensity of C1s measured by ESCA, a is based on CHn (n is an integer of 0 to 3), and b is C—O and C—N. And c is based on COO.)
  Synthetic resinIf the surface functional group ratio R is modified to 47 or more, preferably 47 to 60, the adhesion can be further improved. The functional group ratio R can be adjusted by changing the atmospheric pressure (vacuum degree) if the discharge power and the treatment time are constant. If the atmospheric pressure (vacuum degree) is set low, the functional group ratio R depends on the plasma treatment. The effect of surface modification is increased. Therefore, attachSynthetic resinDepending on the type, if you set the pressure (vacuum) lowSynthetic resinThe surface functional group ratio R can be 47 or more. On the other hand, if the atmospheric pressure (vacuum degree) is too low, the discharge becomes unstable. More specifically, the atmospheric pressure (vacuum degree) is 1.3 × 10 6.^-2~ 9.3 × 10^-2It is preferably about Pa.
[0032]
The discharge power is 1 to 5 W / cm.²The degree is preferred. If the power is too low, sufficient adhesion of the metal thin film may not be obtained, and the processing speed may decrease. If it is too high, the discharge becomes unstable and stable processing may not be possible. The discharge is preferably RF (high frequency) discharge rather than DC (direct current) discharge. The functional group ratio R can be increased by RF (high frequency) discharge. In addition, the processing time of such plasma processing is about several seconds to 1 minute.
[0033]
  If a metal substrate is installed in the vacuum vessel and plasma treatment is performed,Synthetic resinSince the surface of the insulating layer is also modified at the same time,Synthetic resinIf the functional group ratio R of the surface is modified to be 47 or more, for example, when a synthetic resin used for forming the insulating layer is used as a target, the insulating layer is similarly formed on the surface. The functional group ratio R becomes 47 or more, and the adhesion of the surface of the insulating layer can also be improved.
[0034]
  And after such a plasma treatment is made,Synthetic resinA metal thin film is formed by vacuum deposition on the surface of the metal and the surface of the insulating layer to which is attached.
[0035]
In order to form a metal thin film by vacuum deposition, a sputtering method is mainly used, and normal direct current and high frequency sputtering may be used, but magnetron type sputtering with a high deposition rate is preferably used.
[0036]
  In vacuum deposition, for example, using a vacuum vessel, the metal to be deposited (including oxides or nitrides of the metal) and a metal substrate are placed opposite to each other in the vacuum vessel, By applying an atmosphere gas while applying a vacuum, the metal is placed on the entire surface of the metal substrate, that is,Synthetic resin used to form insulating layersCan be deposited on the surface of the metal and the surface of the insulating layer. As an atmospheric gas in vacuum deposition, an inert gas such as argon, neon, xenon, or krypton is preferably used, but industrially, argon is preferably used. The atmospheric pressure (degree of vacuum) is 10^-1To 1.3 Pa, preferably 1.5 × 10^-1~ 8x10^-1It is preferable to set it to Pa.
[0037]
Examples of the metal deposited by vacuum deposition include copper, chromium, nickel, aluminum, silver, gold, titanium, tin, and indium, and the thickness is preferably about 4 to 500 nm. .
[0038]
Moreover, you may vapor-deposit such a metal as a multilayer. For example, if a metal having higher adhesion to the substrate is deposited on the substrate side, the adhesion can be improved. For example, when forming as two layers, chromium, nickel, titanium, an alloy containing two or more of these, or an oxide of these metals is used as the first layer on the substrate side. As the layer, copper, aluminum, silver, gold, tin, and nickel are preferably used.
[0039]
Such plasma treatment and vacuum deposition may be industrially performed continuously using, for example, a treatment apparatus as shown in FIG. That is, in FIG. 1, this processing apparatus includes an electrode roll 2, a plasma electrode 3 disposed opposite to the electrode roll 2, two sputtering deposition electrodes 21 and 22, and an electrode roll 2 in a vacuum container 1. In contrast, the unwinding shaft 4 and the unwinding shaft 5 disposed on the opposite side of the plasma electrode 3 and the two sputter deposition electrodes 21 and 22, and the unwinding shaft 4 and the electrode roll 2 are disposed. Two unwinding side guide rolls 6 and 7, and two unwinding side guide rolls 8 and 9 disposed between the winding shaft 5 and the electrode roll 2.
[0040]
A long base material 10 is wound around the unwinding shaft 4, and the base material 10 is unwound by the unwinding shaft 4, and the electrodes are disposed along the unwinding side guide rolls 6 and 7. After being guided by the roll 2 and moved along the outer peripheral surface of the electrode roll 2, it is guided to the take-up shaft 5 along the take-up side guide rolls 8 and 9, and is taken up by the take-up shaft 5. It is configured. In addition to the long base material, even if the base material is a single-wafer type base material, it is treated in the same manner as the long base material by sticking it on a long base material. can do.
[0041]
A high frequency power source 12 is connected to the plasma electrode 3 via a matching circuit 11, and Ti, V, Y, Zr, Nb, Mo, W, Ta, Cr, Ni, An ingot 13 made of a metal composed of one or more of Si, or an oxide or nitride of these metals is provided. More specifically, the plasma electrode 4 is formed in a flat plate shape and facilitates plasma treatment by increasing the density of ions and radicals in order to easily obtain the uniformity of plasma treatment in the width direction of a long base material. In order to improve the efficiency, a planar magnetron type cathode electrode is used. In addition, by placing the ingot 13 on the discharge surface of the plasma electrode 3 in this way, the plasma electrode 3 is prevented from being sputtered with respect to the atmospheric gas. The material is effectively prevented from adhering to the base material 10. As a result, the adhesion between the substrate 10 and the metal thin film can be improved when the metal thin film is formed by vacuum deposition after the plasma treatment. Moreover, even if the discharge power is increased, the ingot 13 is very difficult to be sputtered with respect to the atmospheric gas, so that the plasma processing time can be shortened compared to the conventional case, and the processing efficiency can be improved.
[0042]
  Then, under the plasma treatment conditions described above, the long base material 10 is unwound from the unwinding shaft 4 and moved along the outer peripheral surface of the electrode roll 2, and the plasma electrode 3 is opposed during this movement. While performing the above plasma treatment,Synthetic resin used to form insulating layersAfter the surface of the metal and the surface of the insulating layer are modified, the material is wound around the winding shaft 5.
[0043]
Further, DC power sources 23 and 24 are connected to the two sputter deposition electrodes 21 and 22, respectively, and the above metal ingots 25 and 26, for example, the sputter deposition electrode 21 are connected to the respective discharge surfaces. The copper ingot 25 and the sputter deposition electrode 22 are each provided with a chromium ingot 26.
[0044]
And under the above-described vacuum deposition conditions, the substrate 10 wound around the winding shaft 5 is unwound again and moved in the reverse direction along the outer peripheral surface of the electrode roll 2, and during this movement, For example, first, a metal thin film of an ingot 26 made of chromium is vacuum-deposited while facing the sputter deposition electrode 22, and then on the metal thin film while facing the sputter deposition electrode 21. Then, a metal thin film of the ingot 25 made of copper is vacuum-deposited, and then wound by the unwinding shaft 4.
[0045]
  As a result, plasma processing and vacuum deposition are industrially linked in this processing apparatus.ContinuedCan be processed. One or more sputter deposition electrodes may be provided, and a plurality of plasma electrodes may be provided.
[0046]
Such a method for forming a metal thin film according to the present invention comprises a substrate for a printed circuit board in which a substrate having a metal surface and an insulating layer surface is used on the outermost surface, and the printed circuit board substrate. In a printed circuit board in which a material is used, it is suitably used for forming a metal thin film.
[0047]
That is, in such a printed circuit board substrate or a printed circuit board, in the manufacturing process, a process of forming a metal thin film on the entire surface of the substrate having a metal surface and an insulating layer surface on the outermost surface, Further, the method includes a step of forming a conductor layer as a predetermined pattern on the metal thin film. In the step of forming such a metal thin film, the method for forming a metal thin film of the present invention is applied.
[0048]
More specifically, the method for forming a metal thin film of the present invention is suitably used in the manufacturing process of a suspension board with circuit. That is, the suspension board with circuit is a circuit wiring board in which the wiring for connecting the magnetic head and the read / write board is integrally formed on the suspension board that supports the magnetic head. First, a base layer as an insulating layer is formed in a predetermined pattern on a metal substrate that is a suspension substrate, and then a metal thin film is formed on the entire surface of the metal substrate and the base layer. Includes a step of forming a conductor layer as a predetermined wiring pattern. In the step of forming a metal thin film on the entire surface of the metal substrate and the base layer, the method for forming a metal thin film of the present invention is applied.
[0049]
  An example of the manufacturing process of such a suspension board with circuit will be described with reference to FIGS. 2 and 3. First, as shown in FIG. 2 (a), on a metal substrate 31 made of SUS or the like, FIG. As shown in FIG. 2B, after the base layer 32 as an insulating layer made of polyimide or the like is formed as a predetermined pattern by the method described above, the base layer 32 is formed as shown in FIG. The surface of the metal substrate 31 that is not, Synthetic resin used to form insulating layers33 is attached.
[0050]
  Synthetic resin used to form insulating layersIn order to attach 33, the photosensitive resin film before curing having a predetermined pattern is used as a target to adhere the photosensitive resin to the surface of the metal substrate 31 by the PVD method and to cure the photosensitive resin. It is preferable to carry out in the same process. In this way, the number of processes can be reduced and the production efficiency can be improved.
[0051]
That is, in this method, first, as shown in FIG. 4A, a coating of a photosensitive resin is applied to the entire surface of the metal substrate 31 and dried to form a film 32p, and then FIG. As shown in FIG. 4B, the exposed film is exposed through a photomask 35. If necessary, the exposed portion is heated to a predetermined temperature and then developed as shown in FIG. Are formed as a predetermined pattern. As described above, the photosensitive resin is preferably a polyamic acid, and when the polyamic acid is used, it is preferably developed with a negative type, and in FIG. 4C, the negative type is developed. It is shown.
[0052]
  Then, as shown in FIG. 5D, the metal substrate 31 on which the film 32p having a predetermined pattern is formed is placed in the vacuum vessel 36, nitrogen gas is introduced, and the atmospheric pressure (vacuum) in the vacuum vessel 36 is introduced. Degree) to 0.1-1 Pa. Thereafter, by raising the temperature in the vacuum vessel 36 to 350 to 400 ° C., as shown in FIG. 5E, the molecules of the photosensitive resin forming the coating 32p are scattered from the coating 32p. By keeping the inside of the vacuum vessel 36 at 3 to 20 Pa and 350 to 400 ° C. for 1 to 2 hours, the surface of the metal substrate 31 is uncured.Synthetic resin33 as well as the coating 32p and uncuredSynthetic resin33 is cured, and as a result, as shown in FIG. 2C, the surface of the metal substrate 31 on which the base layer 32 is not formed is formed.Synthetic resin33 is attached.
[0053]
  Then thisSynthetic resin used to form insulating layersAfter performing the above-described plasma treatment on the entire surface of the metal substrate 31 and the base layer 32 to which 33 is attached and modifying the surface, as shown in FIG. 2 (d), by vacuum deposition such as sputtering, The metal thin film 37 is formed by sequentially forming the deposited chromium layer 37a and the deposited copper layer 37b.
[0054]
The metal thin film 37 formed on the metal substrate 31 is removed by chemical etching or the like in a later step. However, in the step of forming the conductor layer 34 described below by plating, the metal thin film 37 is plated on the metal thin film 37. Since the resist 38 is formed, the resist 38 needs to be formed with good adhesion without being peeled off even when immersed in a plating solution.
[0055]
Then, as shown in FIG. 3 (e), a plating resist 38 is formed with a predetermined resist pattern on the metal thin film 37, and as shown in FIG. 3 (f), the plating resist 38 is not formed. A conductive layer 34 having a predetermined wiring pattern is formed on the portion by plating such as electrolytic plating. Thereafter, as shown in FIG. 3G, the plating resist 38 and the metal thin film on which the plating resist 38 has been formed are formed. 37 is removed by chemical etching or the like, whereby the conductor layer 34 is formed on the base layer 32 as a predetermined wiring pattern. Thereafter, as shown in FIG. 3 (h), if a cover layer 39 made of polyimide or the like covering the conductor layer 34 is formed by a known method, a suspension with circuit can be obtained.
[0056]
Such a manufacturing process can be applied not only to the suspension board with circuit but also to other wired circuit boards.
[0057]
In this way, in the suspension board with circuit and the wired circuit board obtained by using the method for forming a metal thin film of the present invention, the adhesion between the base layer and the conductor layer is good, and the conductor layer is formed. In this plating process, even if the metal thin film is immersed in the plating solution, it does not peel off, so that the plating bath can be prevented from being contaminated, and the quality of the suspension board with circuit and wiring circuit board obtained can be prevented from deteriorating. . Therefore, the obtained suspension board with circuit and wired circuit board have high reliability and good quality, and can be used effectively in various fields.
[0058]
Also, in the case of multilayer wiring boards, etc., when it is necessary to form a conductor layer pattern not only on the insulating layer but also on the metal substrate, both conductivity and adhesion between the metal substrate and the metal thin film are compatible. Can be made.
[0059]
Furthermore, in the case of forming a conductor layer pattern on the metal substrate, in order to further improve the adhesion between the metal substrate and the metal thin film, after forming the conductor layer pattern by plating, a vacuum of 200 to 400 ° C. It is effective to heat under. By this heat treatment, the adhesion between the metal substrate and the metal thin film is improved several times or more as compared with before heating.
[0060]
The substrate for a printed circuit board obtained by using the method for forming a metal thin film of the present invention only needs to have a metal surface and an insulating layer on the outermost surface. For example, the metal substrate and the metal substrate It may be composed of two layers of an insulating layer formed as a predetermined pattern on the conductor layer, or may be composed of two layers of a conductor layer and an insulating layer formed as a predetermined pattern on the conductor layer. May be a multilayer wiring circuit board laminated in a plurality of three or more layers.
[0062]
Furthermore, the method for forming a metal thin film of the present invention can also be effectively applied to, for example, manufacturing processes for electrodes of liquid crystal displays, touch panels, electromagnetic wave shields, and the like.
[0063]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
[0064]
Examples 1-8
The circuit wiring board of Examples 1-8 was produced by the manufacturing process which consists of following each process 1) -5). In each of Examples 1 to 8, as shown in Table 1, the pressure during curing (Pa) and the pressure during plasma treatment (× 10^-2Pa) was varied.
[0065]
1) Base material production process
A polyamic acid having the following composition is applied to the following stainless steel long substrate, dried to form a film, exposed through a photomask, the exposed portion is heated, and then a negative type using an alkali developer. The base material in which the polyamic acid film was formed as a predetermined pattern on the surface of the stainless steel substrate was produced by developing the film.
[0066]
In addition, the base material was wound up in roll shape through the spacer. By doing so, an appropriate gap is formed between the wound substrates, so that the polyamic acid adheres smoothly to the surface of the stainless steel substrate in the next step.
[0067]
Stainless steel long substrate: SUS304, width 250mm, thickness 24μm, 250m winding
Photosensitive polyamic acid: Acid dianhydride (3,4 ', 3,4'-biphenyltetracarboxylic dianhydride, 6.5 mol) and diamine (paraphenylenediamine, 3.9 mol and 2,2' -N-methyl-2-pyrrolidone solution of polyamic acid obtained by reacting bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2.6 mol) with a photosensitizer (1,4-dihydropyridine Derivatives) added.
[0068]
2) To the surface of the stainless steel substrateSynthetic resinAdhesion process
  The polyamic acid film having a predetermined pattern is used as a target, and the polyamic acid is attached to the surface of the stainless steel substrate by the PVD method, and at the same time, the polyamic acid film having a predetermined pattern is attached to the surface of the stainless steel substrate. The polyamic acid was cured (imidized) in one step.
[0069]
That is, first, the base material wound up in a roll shape was set in a vacuum heating furnace, the inside of the furnace was evacuated, nitrogen gas was introduced, and the atmospheric pressure in the furnace was reduced to about 1 Pa. Thereafter, the temperature in the furnace was increased from room temperature to 380 ° C. over about 2 hours. At this time, the polyamic acid molecules scattered from the polyamic acid film into the furnace and adhered to the surface of the stainless steel substrate on which no film was formed. At this time, the atmospheric pressure in the furnace rises. However, by adjusting the atmospheric pressure to a predetermined value (5 to 8 Pa) and holding it at 380 ° C. for 2 hours, it adheres to the polyamic acid film and the surface of the stainless steel substrate. The polyamic acid was cured. In addition, the thickness of the polyamic acid adhering to the surface of the stainless steel substrate was adjusted by adjusting the atmospheric pressure.
[0070]
3) Plasma treatment process
Plasma processing was performed using the processing apparatus shown in FIG. A planar magnetron sputter electrode was used as the plasma electrode 3, and a Zr ingot 13 (5 × 15 inches) was mounted on the discharge surface. And after mounting a roll-shaped base material on the winding shaft 4, the inside of the vacuum vessel 1 is 2 × 10 2 by a vacuum pump.^-3The gas is exhausted to Pa, nitrogen gas is introduced, and the atmospheric pressure is set to a predetermined value (2.7 × 10^-2~ 4x10^-1Pa). Thereafter, a high frequency voltage of 13.56 MHz (discharge power: 2 W / cm) is applied to the plasma electrode 3.²) Was discharged, and plasma treatment was performed by running the substrate at 1.5 m / min while winding the substrate with the winding shaft 5.
[0071]
4) Vacuum deposition process
Subsequently, vacuum deposition was performed using the processing apparatus shown in FIG. Planar magnetron sputtering electrodes are used for the two sputtering deposition electrodes 21, 22, a Cu ingot 25 (5 × 15 inches) is used for the sputtering deposition electrode 21, and a Cr ingot 26 is used for the sputtering deposition electrode 22. (5 × 15 inches) were mounted as sputtering targets. Then, argon gas is introduced into the vacuum vessel 1 instead of nitrogen gas, and the atmospheric pressure is 4 × 10.^-1Held at Pa. Thereafter, 2.8 kW and 1.5 kW direct currents are applied to the sputtering deposition electrodes 21 and 22, respectively, to discharge the substrate, and the substrate wound on the winding shaft 5 is reversed from the plasma processing. Then, chromium and copper were continuously vacuum-deposited by running at 1 m / min while winding on the unwinding shaft 4.
[0072]
5) Electrolytic copper plating process
On the vacuum-deposited copper layer, a copper plating layer was formed to a thickness of 10 μm by electrolytic copper plating in a separate process. In Example 8, after the copper plating layer was formed, it was heated under vacuum at 380 ° C. for 2 hours.
[0073]
    Comparative Example 1
  In the base material production step (step 1), a polyamic acid film is formed as a predetermined pattern on the surface of the stainless steel substrate, and then applied to the surface of the stainless steel substrate.Synthetic resinIn the same manner as in Example 1, except that the adhesion step (step 2) was omitted, that is, the polyamic acid film was cured as it was without adhering the polyamic acid to the surface of the stainless steel substrate. A circuit board was produced.
[0074]
In addition, as for the thickness of the formed metal thin film, as for the Example and the comparative example, both the vapor deposition chromium layer was 30 nm, and the thickness of the vapor deposition copper layer laminated | stacked on it was 70 nm.
[0075]
    Evaluation methods
1) Adhered to the surface of the stainless steel substrateSynthetic resinAnalysis of
  After the plasma treatment step (step 3), surface composition analysis was performed using ESCA (Shimadzu / Kratos AXIS-His), and adhesion was observed.Synthetic resinThe thickness and the functional group ratio R were measured. According to ESCASynthetic resinThe thickness d was determined from the following equation. The results are shown in Table 1.
[0076]
d = −λln (I_s/ I_o)
I_s: Signal strength of stainless steel substrate
I_o: Total signal intensity
λ: Mean free path of electrons in solid (λ = 2 nm in this measurement)
2) Measurement of adhesion
For the printed circuit boards of Examples 1 to 8 and Comparative Example 1, the adhesive strength of a) insulating layer (polyimide) / deposited chromium layer and b) stainless steel substrate / deposited chromium layer was measured by a 90 ° peel test.
[0077]
The shape of the measurement sample is 2 mm wide × 100 mm long, and the cutout position of the measurement sample is a total of 3 points, approximately the center of the original fabric width and approximately 50 mm from both ends as shown in FIG. ) Was appropriately cut out, and the average value of the three measured values was defined as the adhesion. The results are shown in Table 1.
[0078]
[Table 1]

  As is clear from Table 1, compared to Comparative Example 1, the surface of the stainless steel substrateSynthetic resinIt can be seen that Examples 1 to 8 to which are attached have improved adhesion b. Moreover, it turns out that the adhesive force a is also favorable. Moreover, it turns out that the adhesive force of Example 7 whose functional group ratio R is 41 compared with the other Examples 1-6, 8 has fallen a little.
[0079]
【The invention's effect】
As described above, according to the method for forming a metal thin film of the present invention, it is possible to form a metal thin film by vacuum deposition while sufficiently improving adhesion on both the metal surface and the surface of the insulating layer. If a substrate for a printed circuit board, a wired circuit board, and a suspension board with circuit are manufactured using such a method for forming a metal thin film according to the present invention, a highly reliable product with good quality can be obtained. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram showing an embodiment of a processing apparatus for performing plasma processing and vacuum deposition according to the present invention.
FIG. 2 is a process diagram showing an example of a manufacturing process of a suspension board with circuit,
(A) is sectional drawing which shows the metal substrate which is a suspension board,
(B) is a cross-sectional view showing a step of forming a base layer as a predetermined pattern on a metal substrate;
(C) on the surface of the metal substrate on which the base layer is not formed,Synthetic resin used to form insulating layersSectional drawing which shows the process of attaching
(D) shows sectional drawing which shows the process of forming a vapor deposition chromium layer and a vapor deposition copper layer one by one by vacuum vapor deposition.
FIG. 3 is a process diagram illustrating an example of a manufacturing process of the suspension board with circuit, following FIG. 2;
(E) is sectional drawing which shows the process of forming a plating resist by a predetermined resist pattern on a metal thin film,
(F) is a cross-sectional view showing a step of forming a conductor layer of a predetermined wiring pattern by electrolytic plating on a portion where no plating resist is formed,
(G) is a cross-sectional view showing a step of removing the plating resist and the metal thin film on which the plating resist has been formed by chemical etching;
(H) is sectional drawing which shows the process of forming the cover layer which consists of a polyimide etc. which coat | covers a conductor layer by a well-known method.
4 (c), on the surface of the metal substrate on which the base layer is not formed,Synthetic resin used to form insulating layersIt is a process diagram for explaining the process of attaching,
(A) is sectional drawing which shows the process of forming the film | membrane of the photosensitive resin on the whole surface of a metal substrate,
(B) is sectional drawing which shows the process exposed through a photomask,
(C) is sectional drawing which shows the process to develop.
FIG. 5 is a cross-sectional view of the surface of the metal substrate on which the base layer is not formed in FIG.Synthetic resin used to form insulating layersIt is a process diagram for explaining the process of attaching,
(D) is a cross-sectional view showing a step of depressurizing a metal substrate on which a film having a predetermined pattern is formed in a vacuum vessel;
(E) scatters the molecules of the photosensitive resin forming the film from the film and attaches it to the surface of the metal substrate;Synthetic resinIt is sectional drawing which shows the process of hardening | curing.
FIG. 6 is an explanatory diagram for explaining a sample used for measuring an adhesion force.
[Explanation of symbols]
  31 Metal substrate
  32 Base layer
  33Synthetic resin
  37 Metal thin film

Claims (2)

An insulating layer is formed as a predetermined pattern on the metal substrate, and a base material having a metal surface and an insulating layer surface, or a metal is formed as a predetermined pattern on the insulating layer, and the metal surface And a base material having a surface of an insulating layer, a method of forming a metal thin film by vacuum deposition,
A method for forming a metal thin film, characterized in that a synthetic resin used for forming an insulating layer is attached to the surface of the metal in advance and subjected to plasma treatment before vacuum deposition. 2. The method for forming a metal thin film according to claim 1, wherein the functional group ratio R represented by the following formula (1) on the surface of the synthetic resin used for forming the insulating layer is 47 or more.
R = (b + c) / a (1)
(In the above formula (1), a, b and c represent the spectral intensity of C1s measured by ESCA, a is based on CHn (n is an integer of 0 to 3), b is C—O and C—N. And c is based on COO.)

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