JPH0719949B2 - Flexible wiring board manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a flexible wiring board.

[Prior Art] Flexible wiring boards are widely used in the field of electronic devices because they are highly flexible and thin. But,
The conventional method for manufacturing a flexible wiring board has a complicated manufacturing process, and the flexible wiring board manufactured by the conventional method has a drawback inevitably caused by the manufacturing method.

Referring to FIGS. 4 (a) to (h) and FIGS. 5 (a) to (h), the conventional method for manufacturing a flexible wiring board having a terminal portion as shown in FIG. I will explain later.

4 (a) to 4 (h) are sectional views in the direction perpendicular to the wiring pattern in the central portion of the wiring board, and FIGS. 5 (a) to 5 (h) are sectional views in the same direction at the end portions of the wiring board.

The copper layer 3 is provided on one surface of the base film 1 by the adhesive 2.
Are adhered (FIG. 4 (a), FIG. 5 (a)). Usually, a polyimide film or a polyester film 1 is coated with an adhesive 2 having an appropriate thickness, dried in a hot air oven or the like, and a copper foil 3 is heated and rolled to bond them.

A resist 4 is formed in a desired pattern on the adhered copper layer 3 (FIGS. 4 (b) and 5 (b)).

The copper layer 3 is etched using an appropriate etching solution (FIGS. 4 (c) and 5 (c)). The remaining resist 4 is peeled off using a stripping solution (fourth step).
(D) and FIG. 5 (d)) A coverlay film 6 is attached to a necessary portion of the surface on the copper side with an adhesive 5 (FIG. 4 (e)). In addition,
If the coverlay film is not adhered to the terminal,
It is shown in FIG.

In order to corrode the insulating layer and expose the copper layer 3, film etching resists 7 and 8 are formed on the cover lay film 6 and the portion to be protected of the base film 1 (fourth).
(F) and (f) of FIG. 5) Corrosion of a predetermined portion of the base film 1 and the cover lay film 6 by a corrosive liquid to remove them (FIG. 4 (g), 5).
(Figure (g)). When the base film 1 and the coverlay film 6 are polyimide films, hydrazine or the like is used as the corrosive liquid.

The remaining resists 7 and 8 are removed by using a stripping solution (FIGS. 4 (h) and 5 (h)). Thus, the conventional method requires many steps, and the insulating layer and the conductor are removed. Since they are bonded by an adhesive, the flexible wiring board made by the conventional method cannot overcome the drawbacks caused by this adhesive, such as the decrease in heat resistance and the etching failure of the adhesive when the insulating layer is etched. It was

[Problems to be Solved by the Invention] It is an object of the present invention to solve the above-mentioned conventional drawbacks and to provide a method of manufacturing a flexible wiring board having excellent reliability.

[Means for Solving Problems] In order to achieve such an object, in the present invention,
A flexible wiring board is manufactured without using an adhesive between the insulating layer and the conductor layer.

That is, the present invention includes a step of forming a photoresist pattern on a metal thin plate, a step of forming a conductor pattern using the photoresist pattern on the metal thin plate, and the entire surface of the metal thin plate on the side having the conductor pattern. First
Forming an insulating layer by coating, removing the thin metal plate, forming a second insulating layer over the entire surface from which the thin metal plate has been removed, and forming first and second insulating layers. The method is characterized by including a step of forming a resist pattern for etching on the layer and a step of removing the first and second insulating layers by etching.

[Operation] As described above, according to the present invention, a flexible wiring board can be manufactured by a simple process, and no adhesive is present between the conductor layer and the insulating layer of the manufactured flexible wiring board. , There are no quality defects due to the adhesive.

[Example] The manufacturing method of the present invention will be described below with reference to FIG. 1 (a) by taking as an example the manufacturing of a flexible wiring board having a conductor terminal portion at one end.
-(H), FIGS. 2 (a)-(h), and FIG.

FIG. 3 is a plan view of a flexible wiring board manufactured by the method of the present invention, in which 13 is a conductor, 13A is a terminal portion of the conductor, and 14 is an insulating layer. 1 (a) to 1 (h) show the situation of the printed wiring board in each step of the present invention along the line X in FIG.
The figure shown about the cross section along -X, and FIG.
FIG. 3H is a view similarly showing the condition of the terminal portion in each step with respect to a cross section taken along the line YY of FIG.

Step 1: forming a photoresist pattern 12 for forming a conductor pattern having a desired shape on the thin metal plate 11 (FIGS. 1A and 2A).

Step 2: A metal pattern such as copper for forming a conductor layer is plated on a portion of the surface of the metal thin plate 11 which is exposed without being covered with the resist pattern 12 to form a conductor pattern 13 (FIG. 1 (b)). , FIG. 2 (b)).

Step 3: The first insulating layer 14 is coated on the surface of the thin metal plate 11 having the conductor pattern 13 (FIG. 1 (c), second).
Figure (c)).

Step 4: The thin metal plate 11 is removed by, for example, etching (FIGS. 1 (d) and 2 (d)).

Step 5: A second insulating layer 15 is coated on the surface from which the metal thin film has been removed (FIGS. 1 (e) and 2 (e)).

Step 6: Form etching resist layers 16 and 17 on the portions of the insulating layers 14 and 15 to be protected in order to corrode the insulating layers 14 and 15 and expose the conductor pattern 13 (FIGS. 1 (f) and 2 (F)).

Step 7: Corrosion removal of predetermined portions of the insulating layers 14 and 15 with a corrosive solution (FIGS. 1 (g) and 2 (g)).

Step 8: If necessary, the remaining resist layers 16 and 17 are removed using a stripping solution (FIGS. 1 (h) and 2 (h)).

Thus, as shown in FIG. 3, a flexible wiring board having the conductor terminal portion 13A at one end is manufactured.

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 As an example of the present invention, a method of manufacturing a flexible wiring board having the terminal portion 13A shown in FIG. 3 will be described.

A negative resist "Microresist 747" manufactured by Eastman Kodak Co., Ltd. was applied onto an aluminum thin plate having a thickness of 80 μm so that the film thickness was 5 μm. The resist-coated aluminum plate was pre-baked, exposed through a high-pressure mercury lamp through the pattern of the wiring board, developed using a dedicated developer and rinse solution, and then post-baked to form a resist pattern on one surface of the aluminum thin plate.

Next, electrolytic copper plating was carried out using a copper pyrophosphate plating bath with the aluminum thin plate on which the resist pattern was formed as the cathode. The conductor pattern obtained has a conductor width of 20.
The conductor spacing was 0 μm, the conductor spacing was 250 μm, and the conductor thickness was 40 μm.

After that, a polyimide resin "U varnish" manufactured by Ube Industries, Ltd. was coated on the entire surface, dried and cured to obtain an insulating layer having a thickness of 20 μm. The aluminum sheet was then etched away with 10 weight percent hydrochloric acid.

Then, the back surface was also coated with "U varnish", cured and dried to form an insulating layer. After that, using "Microresist 747", it is exposed through a pattern mask to form an etching resist on a predetermined portion, and then the insulating layer is corroded and removed by a hydrazine aqueous solution, and then a resist stripping solution manufactured by Nagase Kasei Co. The resist was peeled off using "N-500" to obtain a flexible wiring board with terminals.
After that, the terminal portion was subjected to a flux treatment, and the solder layer at 280 ° C. was dipped for 5 seconds for solder coating, but no deterioration was observed in the resin layer.

Example 2 Similar to Example 1, after forming a resist pattern on an aluminum thin plate, copper plating was performed to obtain a conductor pattern having a conductor width of 300 μm, a conductor interval of 350 μm, and a conductor thickness of 35 μm.

Then, a solvent-soluble polyamideimide resin synthesized from diamino-diphenyl ether and trimellitic acid chloride was coated, dried and heat-treated to obtain a 30 μm thick insulating layer. Then, the aluminum thin plate was removed by etching with 10% by weight of hydrochloric acid, and the photoresist was stripped using a resist stripping solution "N-500" manufactured by Nagase Chemicals. Again, coat the backside with the solvent-soluble polyamide-imide resin described above, dry and heat-treat
The insulating layer has a thickness of μm.

After that, using "Microresist 747", it is exposed through a pattern mask to form an etching resist on a predetermined portion, and then the insulating layer is corroded and removed by an aqueous solution of hydrazine, and then a resist stripping solution manufactured by Nagase Kasei Co., Ltd. The resist was peeled off using "N-500" to obtain a flexible wiring board with terminals. Then, put it in a solder bath at 300 ° C for 20
After dipping for a second and solder coating was performed, deterioration of the resin layer was not recognized. The adhesive strength and dimensional accuracy were also excellent.

As the conductor metal, any metal can be used as long as it is a metal that can be electroplated, but copper is preferable from the viewpoint of conductivity and economy.

The removal of the thin metal plate can be performed not by etching as in this embodiment but by peeling (peeling off). However, etching is preferable in order not to disturb the conductor pattern, and in the case of etching, one having etching characteristics different from those of the conductor metal is preferable. When copper is used as the conductor metal as in this embodiment, it is preferable to use aluminum, tin, zinc or the like.

It is also preferable to remove the photoresist used for pattern plating of the conductor layer at an appropriate time after the plating is finished, for example, after the plating is finished or after the metal thin plate is removed.

Since the resin is coated, unlike the case where the film is bonded to the metal, the liquid type is coated, so the adhesiveness can be improved without leaving bubbles between the metal and the insulating layer, and external force is applied. Therefore, the dimensional accuracy of the product can be improved.

Since the resin forming the insulating layer is required to have heat resistance and flexibility, there are polyamic acid, polyimide resin, polyamideimide resin, polyester modified imide resin, silicone imide resin, rubber modified epoxy resin and the like. In particular, a solvent-soluble imide group-containing polymer, and further a solvent-soluble polyamide-imide resin are preferable, and those having excellent adhesiveness and dimensional accuracy without pinholes or bubbles are obtained.

In the above-described embodiment of the present invention, the flexible wiring board with a terminal has been particularly described, but one surface of the conductor portion is covered with an insulating layer, and the other surface is not coated, a flexible wiring board including a so-called land portion, It goes without saying that it can be produced by the method of the present invention.

[Effects of the Invention] As described above, according to the present invention, a predetermined conductor pattern is formed on a thin metal plate, a first insulating layer is formed on the upper portion by coating, and then the thin metal plate is removed. Then second
Since the insulating layer is formed by coating and then the insulating layer is pattern-etched, a flexible wiring board having excellent heat resistance and high quality can be manufactured.

[Brief description of drawings]

FIGS. 1 (a) to (h) and FIGS. 2 (a) to (h) are cross-sectional views for explaining an embodiment of the manufacturing process of the flexible wiring board of the present invention, and FIG. 3 is produced by the present invention. A plan view of a flexible wiring board, FIGS. 4 (a) to (h) and FIGS. 5 (a) to (h) are cross-sectional views illustrating a conventional manufacturing method. 1 ... Base film, 2,5 ... Adhesive, 3 ... Conductor, 4 ... Resist, 6 ... Coverlay film, 7,8 ... Film etching resist, 11 ... Metal sheet, 12 ... Photo Resist pattern, 13 ... Conductor pattern, 13A ... Terminal part, 14 ... First insulating layer, 15 ... Second insulating layer, 16, 17 ... Etching resist layer.

Claims (1)

[Claims] 1. A step of forming a photoresist pattern on a metal thin plate, a step of forming a conductor pattern on the metal thin plate using the photoresist pattern, and a surface of the metal thin plate on a side having the conductor pattern. A step of forming a first insulating layer by coating on the entire surface of the substrate, a step of removing the thin metal plate, and a step of forming a second insulating layer by coating on the entire surface from which the thin metal plate has been removed. And a step of forming a resist pattern for etching on the first and second insulating layers, and a step of removing the first and second insulating layers by etching. Method.