JPH0158878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a wiring board that allows a fine pattern to be easily obtained.

(Conventional technology) The line width and line spacing of wiring boards are becoming thinner and thinner as LSIs become more highly integrated. However, in conventional manufacturing methods, for example, when forming a pattern by etching a copper-clad laminate, the processing limit is 100 μm or less, and line widths smaller than this are likely to cause wire breaks and shorts. This is caused by dents, scratches, etc. that occur during the manufacturing process of copper-clad laminates.
Furthermore, when the line spacing becomes about 50 μm, the line width accuracy decreases due to minute irregularities and waviness on the surface of the copper-clad laminate. In addition, the copper foil normally used for such copper-clad laminates is 18 to 35 μm thick, and the thickness of the outermost conductor layer is 50 to 70 μm depending on the plating performed to form the through holes. Therefore, it is difficult to find suitable conditions for etching when the line width is less than 100 μm. If a copper foil with a thickness of 5 to 9 μm is used for the copper-clad laminate, parts such as inner layer circuits where there is no need to form conductors on the copper foil can be etched with high precision. However, the outermost layer has a conductor thickness of 30 to 40 .mu.m due to plating performed to form through holes, and etching with a line width of 100 .mu.m or less is difficult.

For these reasons, the additive method, in which circuits are formed by plating in the necessary areas, rather than the etching method, is suitable for forming fine patterns, but at present the surface of the substrate is very rough, and unnecessary areas are left unattended. There is a copper splatter phenomenon in which attached metal precipitates, and it is not possible to form finer patterns than the subtract method, which forms circuits by etching.

In addition, a semi-additive method can be used in which the necessary parts of a copper-clad laminate using copper foil with a thickness of 5 to 9 μm are marked, and then a quick query is performed to remove only the unnecessary parts of the copper foil. Similar to the copper-clad laminate using thick copper foil, it is difficult to form a fine pattern of 80 μm or less because it is dominated by the defects and characteristics of the copper-clad laminate itself.

Therefore, in recent years, a plating resist 1 is formed in a desired shape on the surface of a conductive holder 2.
A metal layer 4 consisting of a metal layer and another metal layer different from the removal conditions of the holder 2 is formed by plating, the plating resist 1 is removed, and an insulating base material is overlaid on the surface of the metal layer 4. A method of manufacturing wiring boards in which conductor circuits are embedded, which involves pressing together and removing the holder 2 until the metal layer 4 is exposed, has come into widespread use.

(Problem to be Solved by the Invention) However, although the wiring board obtained by this conventional manufacturing method for wiring boards in which conductor circuits are embedded can form fine wiring patterns, as shown in FIG. Furthermore, if the holder 2 has a slight flaw or dent, the plating solution for forming the metal layer 4 may seep into the defect, causing a short circuit.

The present invention provides a method for manufacturing a wiring board that allows a fine pattern to be easily obtained.

(Means for Solving the Problems) The method for manufacturing a wiring board of the present invention involves forming a plating resist 1 in a desired shape on the surface of a conductive holder 2, and forming a first plating resist 1 that can be removed together with the holder 2. A second metal layer 5 is formed by plating, and a second metal layer consisting of a metal layer different from the removal conditions of the holder 2 and another metal layer is formed by plating.
A metal layer 4 is formed by plating, the plating resist 1 is removed, an insulating base material is overlaid and pressure-bonded on the surface of the second metal layer 4, and the process is continued until the second metal layer 4 is exposed. The method is characterized in that both the first metal layer 5 and the holder 2 are removed.

That is, as shown in FIG. 1, small scratches and dents 3 in the holder 2 are filled with metal that can be removed together with the holder 2, and a metal layer that protects the circuit and a metal that becomes a conductor are placed on top of the metal that can be removed together with the holder 2. After forming the layer and burying the metal that will become the circuit in the insulating base material, the holder 2
This removes both the metal that has filled in the small scratches and dents 3 in the holder 2.

The holder 2 used in the present invention may be a copper foil plated on a stainless steel plate or the like in a peelable manner, and
It is also possible to use copper foil that has already been peeled off or rolled copper foil. The first metal layer 5, which can be removed together with the holder 2, is preferably made of the same metal as the holder 2, and has a thickness that can fill slight scratches and dents in the holder 2, as described above. It is usually about 3 μm.

The second metal layer 4 consisting of a metal layer and another metal layer different from the removal conditions of the holder 2 may be gold, nickel, solder, gold and copper, nickel and copper, etc. itself, in the case of two or more types, the removal conditions for the metal facing the first metal 5 are as follows:
It needs to be different from the first metal 5.

Example After polishing the stainless steel surface, the entire surface was plated with copper sulfate to a thickness of 30 μm. Next, after polishing the copper surface with sandpaper, a photoresist was laminated with a roll laminator. After applying a positive mask and irradiating it with ultraviolet rays, a developer was sprayed and developed. Next, copper plating was performed to a thickness of 3 μm to fill in the scratches caused by polishing, gold plating was performed to a thickness of 1 μm, and copper sulfate plating was further performed to a thickness of 30 μm to form a circuit pattern. After the resist was removed by immersion in a resist removing solution and a black oxidation treatment was performed, the patterned copper foil was peeled off from the stainless steel plate. This copper foil was set in a mold that could be positioned using an inner layer plate prepared in advance by an etching method, an adhesive prepreg, and positioning pins, and heated and pressed at 170°C for 2 hours at a pressure of 60 kg/cm ² . Next, the copper on the surface was etched until the built-in gold plating was exposed, producing the desired wiring board. This printed wiring board has a circuit pattern with a line width and line spacing of 40 μm.

(Effects of the Invention) As explained above, the following effects have been achieved by the present invention.

(1) Shoots generated in conventional processes are drastically reduced and yields are improved.

(2) Conventionally, polishing scratches were transferred to the pattern surface, but by filling the scratches with copper plating,
A smoother pattern surface with no defects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the method of the present invention, and FIG. 2 is a sectional view for explaining the conventional method. Explanation of symbols, 1...Resist pattern, 2...
Holder, 3... Scratches and voids due to roughening treatment, 4...
...Second metal layer, 5...First metal layer.

Claims (1)

[Claims] 1 Form a plating resist 1 in a desired shape on the surface of a conductive holder 2, form a first metal layer 5 that can be removed together with the holder 2 by plating, and set the removal conditions for the holder 2. A second metal layer 4 consisting of a metal layer different from the above and another metal layer is formed by plating, the plating resist 1 is removed, and an insulating base material is overlaid and crimped on the surface of the second metal layer 4. A method for manufacturing a wiring board, characterized in that both the first metal layer 5 and the holder 2 are removed until the second metal layer 4 is exposed.