JPH0442594A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To easily form holes into a printed circuit board without crack even when the thickness of an insulating resin substrate is extremely thin by collectively forming required numbers of holes and slits, such as holes for through holes, slit for separating pieces having prescribed dimensions, etc., having prescribed shapes by using a resist for etching the substrate at the time of etching the substrate. CONSTITUTION:A laminated film 3 stuck with copper of >= 5 mum in thickness on both surfaces which is formed in such a way that metallic copper thin films 2 are grown on both surfaces of a flexible resin substrate1 which has a thickness of <= 50 mum and is made of polyimide resin by vacuum deposition method, sputtering method, etc., is used. By performing resist photoengrave after sticking a photosensitive resist 4 to both surfaces of the film 3 and developing the resist, holes 5 for through holes and slits 6 for separating pieces having prescribed dimensions are collectively formed by means of the resist 4. After the copper foil 2 on the film 3 removed from a prescribed part by etching, the photosensitive resist 4 removed and a copper foil pattern which is used as a resist for etching polyimide is formed. Then the holes 5 for through holes and slits 6 for separating pieces are formed by etching the polyimide resin substrate1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a flexible printed circuit board on which electronic components and the like are mounted.

[Prior Art] Various methods for manufacturing flexible printed circuit boards (hereinafter referred to as FPC) have been developed depending on the type of FPC, and one example of this is the manufacturing of a double-sided circuit FPC having through holes. The method will be explained using FIG. 4.

As shown in FIG. 4, in the first step 101, CCL (Coppe
At the same time as forming a CCL substrate, this CCL substrate is cut into a predetermined size in a second step 102. Next, in a third step 103, through holes are drilled in the CCL board using an NC drill router. After the through holes are formed, chemical copper plating and electrolytic plating are performed in a fourth step 104 to form the through holes.

Next, in a fifth step 105, the surface of the copper foil is subjected to surface treatment as a pretreatment for resist plate making for circuit formation, and then a sixth step 105 is performed.
In step 106, a photosensitive resist (dry film) is pasted onto the CCL substrate screen by a lamination method. After that, in the seventh step 107, the artwork created using a CAD tool etc. is used as a circuit pattern for exposure, and the photosensitive resist laminated on both sides of the substrate is baked, and in the eighth step 108, an organic solvent or alkaline solution, etc. Perform resist development using

Next, in a ninth step 109, unnecessary copper foil portions are removed by etching using copper chloride or iron chloride solution as an etchant for removing metallic copper. Thereafter, in a tenth step 110, solder resist ink is applied by screen printing to a predetermined portion of the circuit to form a resist for edge pre-plating (surface treatment), and in an eleventh step 111, edge pre-plating (
surface treatment). Types of edge pre-plating include solder plating, gold plating, and composite plating that performs both solder plating and gold plating (in this case, a separate masking process is required). Then, in the twelfth step 112, the outer shape and holes are punched out of the FPC that has been surface-treated using a highly accurate die that has been subjected to NC wire cutting. Finally, in a 13th step 113, a coverlay film is attached to the CCL substrate cut to the above-mentioned outline according to the application.
A PC board is formed, and in a fourteenth step 114, the formed F
The FPC board manufacturing process is completed by inspecting the PC board.

[Problems to be Solved by the Invention] By the way, polyimide resin having a thickness of 75 μm to 125 μm is conventionally used in many cases as a material used for the above-mentioned FPC board. However, in recent years, extremely thin base materials with a thickness of 50 μm or less (for example, a copper foil portion of 18 μm and an insulating base material thickness of approximately 25 μm) have been required for the purpose of providing flexibility and reducing the cost of base materials. ing.

As the thickness of the base material becomes thinner, if you try to drill through holes in the board using an NC drill router, etc., there is a problem that the drilling will cause cracks in the base material during processing. .

Furthermore, even if through-holes can be formed without cracking, because FPCs are used in a variety of ways, many round holes and irregularly shaped through-holes with different diameters will be formed on the substrate. Since these holes must be formed by cutting the base material using a routing operation using a drill machine, it takes a lot of time to process a board that uses many through holes.

Furthermore, in the process of shaping the base material after surface treatment (plating treatment) using a mold and punching holes,
Similarly, if the thickness of the base material becomes extremely thin, not only will there be a problem that cracks will occur during processing, but the external shape of the base material is often complex, and moreover, the upper mold A shown in Fig. 5 Since the clearance C between the mold B and the lower die B must be made extremely small, the mold machining relies on high-precision NC wire cutting, which requires repeated adjustments. Moreover, by repeating punching, the upper die A and the lower die B wear out and the clearance C between them increases, which makes it difficult to cut the substrate F, resulting in an extended portion f as shown in FIG. is formed. For this reason, not only must the mold be made of a material with high wear resistance, but also the mold must be replaced more frequently. Therefore, there is also the problem that the mold becomes expensive and the punching cost becomes extremely high.

As described above, with conventional substrate manufacturing methods, it is difficult to manufacture a substrate with an extremely thin thickness of 50 μm or less.

The present invention has been made in view of these problems, and its purpose is to provide a circuit printed circuit board that can be easily drilled without cracking even if the thickness of the base material is extremely thin. The purpose is to provide a substrate.

Another object of the present invention is to provide a circuit printed board that can be easily processed even when the base material has a complicated external shape and a large number of holes, and can be manufactured at low cost.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a circuit print made of a laminated film in which a thin metal film is formed on an insulating resin base material, and in which a predetermined circuit pattern is formed. In the manufacturing method of the substrate, a resist plate is made on the surface of the metal thin film, and a predetermined portion of the metal thin film is etched away using the plate-made resist to form a resist for etching the insulating resin base material. It is characterized in that a predetermined number of holes and slits of a predetermined shape, such as holes for through holes and slit holes for cutting the outer shape, are formed at once when etching the base material using a material etching resist.

As the insulating resin base material, for example, a polyimide resin having a thickness of 50 μm or less is used, and as the metal thin film, for example, a copper foil having a thickness of 5 μm or more is used.

[Function] According to the method for manufacturing a printed circuit board of the present invention having such a configuration, holes and slits such as holes for through holes and slits for cutting external shapes are formed all at once during etching, so that through holes of various shapes can be formed. A printed circuit board having a large number of holes, a printed circuit board having an extremely discrete external shape, or a printed circuit board having both of these flanges can be manufactured very easily in a short time.

Also, in that case, drilling the board by drilling or punching the board does not involve processing or shaping the board, so even if the board is made thinner, there will be no cracking or poor cutting. Furthermore, since the expensive molds that are conventionally used by high-precision NC wire cutting are not required, circuit printed boards can be manufactured at low cost.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a double-sided circuit flexible printed circuit board, and is a sectional view showing the manufacturing process of the board, and FIG. 2 is a diagram showing the flow of the manufacturing process.

First, as shown in FIG. 2, a laminated film to be used in the first step 101 is selected. As shown in FIG.
After growing several thousand angstroms of metallic copper thin film 2.2 on both sides of the substrate by vacuum evaporation or sputtering, copper is deposited to a thickness of 5 μm by electroless copper plating and electrolytic copper plating. Use double-sided silver-adhesive laminated film 3, or use 1 oz (35 μm t)
JL3/4 oz (27μmt)! Or 1
A polyimide resin is cast on an electrolytic copper foil 2 or a rolled copper foil 2 having a thickness of /2 oz (18 μmt) or the like, and then laminated with a polyimide resin to form a double-sided copper-clad laminate film (for example, "Nisbanek" [registered trademark]). ], etc.) 3 is used. These laminated films 3 are all formed as non-adhesive three-layer laminated films made of copper and polyimide resin.

Next, in a second step 102, this laminated film 3 is cut to a predetermined size, and then in a third step 103, a photosensitive resist (dry film) 4 is applied to the laminated film 3 using a laminator, as shown in FIG. Both sides are laminated and resist plate making is performed, and in a fourth step 104, resist development is performed by exposure and development, and through-hole holes 5 and outline cutting slits 6 are created at once using the photosensitive resist 4.

Next, in a fifth step 105, as shown in FIG. A silver foil pattern used as a resist for polyimide etching is then formed. Then, as shown in Figure 1 (■), using hydrazine as an etchant, the temperature was 40'C and the spray pressure was 2.5°C.
The polyimide resin base material 1 is etched for 10 to 20 minutes under etching conditions of kg/cm 2 to form holes 5 for through holes and slits 6 for cutting the outer shape. In that case,
As shown in FIG. 3, the slits 6 for cutting the outer shape are formed intermittently except in a portion a of the polyimide resin base material 1 and the copper foil 2. Thereafter, in the sixth step 106, a catalyst 7 such as palladium is applied to the entire surface of the laminated film 3 as shown in FIG. Copper panel plating 8 is applied to the entire surface.

After that, in the seventh step 107, as shown in FIG.
Resist plates are formed on both sides of the laminated film 3 using the same method as described above to form etching resists 9 for forming circuit patterns and through holes.

After that, in the eighth step 108, the artwork created using a CAD tool or the like is used as a circuit pattern for exposure, and the photosensitive resist laminated on both sides of the substrate is baked, and the resist is developed using an organic solvent or an alkaline solution. conduct.

Next, in a ninth step 109, the surface of the copper foil 2 is subjected to surface treatment as a pretreatment for resist plate making for circuit formation, and then the first step 109 is performed.
In step 110, as shown in FIG. 1, both sides of the laminated film 3 are spray etched with copper chloride etchant or iron chloride etchant in the same manner as shown in FIG.
As shown in (2) in the figure, the resists on the front and back surfaces of the laminated film 3 are peeled off to form an FPC board 12 having double-sided circuit patterns 10 and through holes 11.

After that, in an eleventh step 111, solder resist ink is printed and applied to a predetermined part of the circuit by a screen printing method or the like.
Along with forming a resist for edge pre-plating (surface treatment),
In a twelfth step 112, edge pre-plating (surface treatment) is performed. Types of edge pre-plating include solder plating, gold plating, and composite plating in which both solder plating and gold plating are performed, similar to the conventional method described above. And the thirteenth step 113
The coverlay film 13 is attached to the laminated film 3 according to the application to form the FPC board 12, and in the fourteenth step 114, the formed FPC board 12 is inspected to complete the manufacturing process of the FPC board 12. .

In the FPC board 12 formed in this way,
As shown in FIG. 3, a portion a of the copper foil 2 and the polyimide resin base material 1 functions as an external support bar to support the circuit pattern 10.
and the through hole 11 are supported by the outer frame 14. The thickness of the copper foil 2 and part a of the polyimide resin base material 1, which are the external support bars, have become extremely thin due to etching. It can be easily cut. Therefore, no cracks will occur in the FPC board 12 during this cutting, and no elongated portions will be formed due to the cutting.

As described above, according to the manufacturing method of this embodiment, in particular, the thickness of 50 μm
The following extremely thin circuit printed circuit boards can be manufactured with high precision and easily, and it becomes possible to fully meet the recent demand for thinner boards.

Note that the present invention is not limited to the above-described embodiments, and various design changes are possible.

For example, in the above-mentioned embodiment, a manufacturing method for a double-sided circuit FPC board 12- having a through hole 11 was described, but it goes without saying that the present invention can be similarly applied to a single-sided circuit FPC board.

In addition, alignment marks (not shown) for exposure are provided during the process of forming through-hole holes 5 and outline cutting slits 6.
can also be formed. By forming this alignment mark for exposure, it becomes possible to dramatically improve the positional accuracy of the front and back resist plates for forming the circuit pattern 10 and the through holes 11.

[Effects of the Invention] As is clear from the above description, the present invention can be applied to circuit printed circuit boards having a large number of holes such as through holes of various shapes, and circuits having extremely complicated external shapes. A printed circuit board or a circuit printed circuit board having both of these can be manufactured very easily in a short time.

Further, in that case, since drilling of the substrate by drilling and punching of the substrate does not involve machining and contouring of the substrate, cracks will not occur even if the substrate is made extremely thin.

Furthermore, since the expensive molds that are conventionally used by high-precision NC wire cutting are not required, circuit printed boards can be manufactured at low cost.

Furthermore, by forming the alignment marks for exposure all at once when etching the base material, the positional accuracy of the front and back resist plates for forming circuit patterns and through holes can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an embodiment of the method for manufacturing a printed circuit board according to the present invention, FIG. 2 is a diagram showing the flow of the method for manufacturing a printed circuit board in this embodiment, and FIG.
The figure is a perspective view showing an FPC board manufactured according to this embodiment, and FIG. 4 is a diagram showing the flow of a conventional FPC manufacturing method.
FIG. 5 is a diagram illustrating the disadvantages that occur when manufacturing an extremely thin FPC using a conventional FPC manufacturing method. PC board shape printing patent

Claims (2)

[Claims] (1) In a method for manufacturing a circuit printed circuit board consisting of a laminated film with a metal thin film formed on an insulating resin base material and on which a predetermined circuit pattern is formed, resist plate making is performed on the surface of the metal thin film, and plate making is performed. A resist for etching the insulating resin base material is formed by etching away a predetermined portion of the metal thin film using the resist for etching the insulating resin base material, and using this resist for etching the insulating resin base material, a slit hole for cutting the outline of a hole for a through hole, etc. is formed. A method for manufacturing a printed circuit board, characterized in that holes and slits of a predetermined shape are formed all at once during etching of a base material. (2) The method for manufacturing a circuit printed board according to claim 1, wherein a polyimide resin having a thickness of 50 μm or less is used for the insulating resin base material, and a copper foil having a thickness of 5 μm or more is used for the metal thin film.