JP2007009301A - Method for producing copper-coated polyimide substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method for making the height of projecting defective parts fixed even with the lapse of time. <P>SOLUTION: In the method for producing a copper-covered polyimide substrate by subjecting a polyimide substrate 1 whose surface has electric conductivity to copper plating by an electroplating process, each carrier roller 2 used in a copper plating liquid upon the electroplating has a shape where both the edge parts have the same large diameter parts 2-2, 2'-2, and the central part has a small diameter part 2-1, and also, only the insides of the large diameter parts 2-2, 2'-2 on both the edge parts in the carrier roller 2 are contacted with both the edge parts in the substrate 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a copper-coated polyimide substrate using a plating method.

Conventionally, a copper-coated polyimide substrate is provided with conductivity by forming a conductive thin film on the surface of a polyimide film having no conductivity by wet plating such as dry plating or electroless plating such as vapor deposition or sputtering, It is obtained by plating copper to a desired thickness on the conductive thin film by electroplating.
For example, Patent Document 1 proposes a method for manufacturing a copper-coated polyimide substrate using electroless plating.

The copper-coated polyimide substrate manufactured in this way is used to manufacture electronic components such as COF printed circuits (Chip On Flexible Printed Circuit) and FPC printed circuits (Flexible Printed Circuit) by forming circuits by photolithography. Widely used as a material for
For example, Patent Document 2 discloses a method for manufacturing a flexible substrate using a copper-coated polyimide substrate.

  By the way, when a circuit is formed on a copper-coated polyimide substrate using a photolithography method, if a convex defect exists in the polyimide film, the convex defect causes uneven exposure and etching. For this reason, it is required that the convex defects on the surface of the polyimide substrate be as low as possible.

In recent years, the demand for higher wiring density has required a reduction in the thickness of the copper layer, which is the conductive layer on the surface of the copper-coated polyimide substrate, and in recent years, the thickness has become around 10 μm. If the thickness of the copper layer is reduced to this level, the leveling effect due to electroplating will be insufficient, and it will become conductive to convex objects of about 1 to 2 μm and the polyimide film due to the exposure of the filler contained in the polyimide film. Under the influence of convex traces of about 1 to 2 [mu] m generated when applying a copper, a problem arises that it is difficult to obtain a copper-coated polyimide substrate having a smooth surface.
In order to solve such a problem, for example, in Patent Document 3, a leveling property is improved by adding a brightener to a copper plating solution.
JP 05-090737 A JP 05-021515 A Japanese Patent Laid-Open No. 06-132634

  However, when a copper-coated polyimide substrate was produced using a copper plating solution to which such a brightener was added, there was a problem that the height of the convex defect portion on the surface of the polyimide substrate increased with the passage of time. .

  The present invention has been made to correct such a problem, and an object of the present invention is to provide a copper plating method capable of making the height of a convex defect portion constant over time.

  As a result of intensive studies, the present inventors have found that the convex defect portion is adsorbed by the additive component on the surface of the transport roller that contacts the entire surface of the polyimide substrate in the plating solution during substrate production, which is the substrate. It has been found that the growth of the convex defect portion is promoted by being transferred to the surface, and the present invention has been adopted.

That is, in the method for producing a copper-coated polyimide substrate according to the present invention, a method for producing a copper-coated polyimide substrate by performing copper plating by electroplating on the surface of a polyimide substrate imparted with conductivity to the surface, The transport rollers used in the copper plating solution when performing electroplating are rollers having a shape in which both ends are the same diameter and a central portion is a small diameter, and both ends of the transport rollers. Only the inside of the large-diameter portion of the portion is in contact with both end portions of the substrate.
Further, in another method for producing a copper-coated polyimide substrate according to the present invention, the contact width W between the large-diameter portion of the transport roller and the end of the substrate is 15 mm or more, and the large-diameter portion and the small-diameter portion of the transport roller The diameter difference h is 2 mm or more.

  According to the present invention, the time-dependent growth of the convex defect portion in the height direction is suppressed, and the height of the convex defect portion can always be made substantially constant.

If this invention is demonstrated based on an accompanying drawing, first, as shown to Fig.1 (a), the copper covering polyimide substrate 1 immersed in the plating solution will be conveyed by the conveyance roller 2. FIG. Then, an anode 4 is provided above the copper-coated polyimide substrate 1 via a rectifier 3, and copper-coated plating is performed using the copper-coated polyimide substrate 1 as a cathode.
As shown in FIG. 1 (b), the transport roller 2 in the present invention is a roller having a substantially H-shaped cross section, more specifically, large diameter portions 2-2, 2′- having the same diameter at both ends. 2 and a roller having a shape in which a small-diameter portion 2-1 is provided at the center, and the large-diameter portions 2-2 and 2'-2 are in contact with both ends of the copper-coated polyimide substrate 1. The contact width (W) in the axial direction or the width direction of the large-diameter portions 2-2, 2′-2 with respect to the substrate 1 is 15 mm or more, and the depth (d) of the annular recess is 2 mm or more. preferable. The reason why the contact width (W) and the depth (d) of the annular recess are limited as described above will be described later.

As the electrolytic copper plating method performed in the present invention, a known method may be used. For example, a common copper sulfate bath is used as the plating bath, and a copper-based consumable anode is used as the anode 4.
In addition, the method for producing the polyimide substrate 1 having conductivity imparted to the surface used in the present invention is not particularly limited, and can be obtained by performing vapor deposition, sputtering, ion plating, electroless plating, etc. on the polyimide film surface. it can.
Although the conveyance roller 2 used by this invention needs to be set as the above shapes, the material is not specifically limited, It can determine suitably according to plating conditions etc.

A copper coating having a thickness of 0.1 μm was formed on one surface of a polyimide film having a thickness of 35 μm by sputtering. The height of the convex defect at that time was measured and found to be 2 μm at the maximum. With respect to the relationship between the shape of the transport roller and the growth in the height direction of the convex defect at that time, the polyimide film provided with conductivity is subjected to electrolytic copper plating with a thickness of 8 μm in a state where the shape of the transport roller is changed. Study was carried out.
In addition, the plating solution composition used in Table 1 and the plating conditions are shown in Table 2.

As described above, the contact width (W) between the large-diameter portions 2-2, 2′-2 at both end portions of the transport roller 2 and the vicinity of both end portions in the width direction of the copper-coated polyimide substrate 1 is copper in the plating step. This affects the transportability of the coated polyimide substrate. Therefore, Table 3 shows the results of investigation on the influence.
When the contact width (W) between the large-diameter portions 2-2, 2'-2 of the transport roller 2 and the vicinity of both ends of the copper-coated polyimide substrate 1 is less than 10 mm, the meandering at the time of transporting the copper-coated polyimide substrate results in FIG. The problems as shown in a) and (b) occur, causing wrinkles and wrinkles on the surface of the polyimide substrate 1. From this, it is understood that the contact width (W) of the transport roller / polyimide substrate may be 15 mm or more.

  Next, the depth (d) of the small diameter part 2-1 at the center part of the transport roller was examined. The contact width (W) of the roller / substrate was fixed at 15 mm. Table 4 shows the results. The change of the height of the convex defect part before and after plating for 120 hours was investigated. As a result, when the depth (d) of the small diameter part 2-1 is 2 mm or more, the height of the convex defect part is suppressed.

  As described above, according to the present invention, the time-dependent growth of the convex defect portion in the height direction is suppressed, and the height of the convex defect portion can always be made substantially constant.

It is a schematic diagram which shows the manufacturing method of this invention, (a) is a figure which shows a manufacturing method schematically, (b) is a figure which shows the conveyance roller used by this invention. It is a figure which shows the relationship between a conveyance roller and a copper covering polyimide board | substrate, (a) And (b) is a figure which shows each state at the time of problem occurrence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copper covering polyimide board 2 Conveyance roller 2-1 Small diameter part 2-2, 2'-2 Large diameter part 3 Rectifier 4 Anode W Contact width d Depth

Claims (2)

In the method of manufacturing a copper-coated polyimide substrate by performing copper plating by electroplating on the surface of the polyimide substrate imparted with conductivity on the surface,
The transport roller used in the copper plating solution when performing the electroplating is a roller having a shape in which both end portions have a large diameter portion having the same diameter and a central portion has a small diameter portion, and A method for producing a copper-coated polyimide substrate, wherein only the insides of the large-diameter portions at both ends are in contact with both ends of the substrate.   The contact width W between the large diameter portion of the transport roller and the end portion of the substrate is 15 mm or more, and the diameter difference h between the large diameter portion and the small diameter portion of the transport roller is 2 mm or more. Of manufacturing a copper-coated polyimide substrate.

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