JPS6338805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible thin keyboard switch member having a spacer printed thereon, and more particularly to a contact part whose main feature is that the spacer is printed and applied, which is mainly used for keyboard switches in electrical equipment. The present invention relates to a method of manufacturing a copper-etched flexible printed circuit board having a pair of circuit parts and a copper-etched flexible printed circuit board.

A conventional method for manufacturing this type of flexible thin keyboard switch member, that is, a keyboard switch board, includes, for example, as shown in FIGS. 1 to 3, a gold-plated circuit 1 formed on a copper-clad phenol laminate 1; It is combined with conductive rubber 3 as a contact portion. In this method, first gold plating 4
Further, the cost is very high and the manufacturing process is also very complicated.
In addition, a copper-clad phenol laminate is used for the substrate. Therefore, it lacks flexibility, and it is difficult to make it thin. A polyester film cut into a predetermined shape (see Fig. 3) is used as a spacer layer 6 between the gold-plated circuit board 1 and the conductive rubber contacts 3, and this is also used for this keyboard switch board. This made manufacturing more complicated.

That is, in the conventional method, a polyester film is cut to a predetermined size separately from the printed circuit board 1 as a spacer 3, and when assembling the device, there is no spacer between the contact printed circuit board 1' and the circuit printed circuit board 1 or between the contact section and the circuit section. It is set by . This process requires two steps: manufacturing the flexible printed circuit board 1 and manufacturing the spacer polyester film molded product 6, and cutting the spacer polyester film 6 requires precision and large dimensions. Furthermore, polyester itself has a problem in terms of elasticity when used as a spacer 6 for a keyboard switch. Therefore, the present invention was devised to reliably eliminate such drawbacks, and it prints highly elastic chloroprene rubber, silicone rubber, flexible epoxy, etc. on a copper-deposited polyester substrate on which contact circuits have already been printed. The flexible printed circuit board and spacer are integrated by painting and etching.

This manufacturing method significantly simplifies the manufacturing process and allows a spacer with elasticity suitable for keyboard switches to be obtained. A copper-etched flexible printed board can be obtained which is easier to manufacture than the conventional method and is more suitable for the purpose.

The present invention provides a method for manufacturing a copper-etched flexible printed circuit board having such characteristics. That is, in this method, a special graphite conductive paint is printed on a copper-deposited polyester film substrate to form a contact part, and a spacer layer is also formed by printing a liquid of chloroprene rubber, silicone rubber, and flexible epoxy. This is achieved by a very simple manufacturing process, such as molding according to a predetermined process. The completed substrate is highly flexible and lightweight, and can significantly reduce costs. In addition, since rubber or elastic synthetic resin is used for the spacer layer,
Highly elastic as a substrate for keyboard switches.

In conclusion, as described above, the present invention provides a copper-etched flexible printed circuit board for a keyboard switch, that is, a thin flexible keyboard switch member, which has various features through a manufacturing process that is extremely simple compared to the conventional method. The present invention aims to provide a method for manufacturing.

In the present invention, first, (a) 20 to 80% by weight of a mixed fine powder of graphite powder with a particle size of 0.1 to 60μ and carbon black powder with a particle size of 0.1μ or less, (b) a polyurethane resin,
A rubber system consisting of one or more of chloroprene rubber, polyester resin, and phenolic resin,
Thermoplastic and thermosetting resin binder 5-30% by weight
and (c) 15 to 80% by weight of a solvent such as dimethylformamide, diethyl carbitol, butyl carbitol, isophorone, and turpentine oil (a+b+
c) Dissolved and uniformly dispersed apparent specific gravity 0.9~
1.5. Prepare a special conductive paint for etching resist with a viscosity of 150 to 10,000 poise.

Using this etching resist suspension, desired patterns of contacts 13 and circuits 14 are formed individually or simultaneously on the copper layer 12 of the flexible polyester film substrate 11 with a thickness of 50 to 150 μ and a copper vapor deposition thickness of 0.2 to 1.0 μ. After printing by screen printing method (see Figures 4a and 4b), the temperature is 95~150℃ for 5~
Dry for 20 minutes [Step (A)].

However, in the composition (a+b+c) of the suspension for etching resist, the quantity limitation in the composition of graphite and carbon black, that is, 20
If the upper and lower limits of ~80% by weight are exceeded, both the so-called "glue" and "consistency" of the stability of the etching resist suspension used for printing will deteriorate.
In particular, if it is less than the lower limit, the conductivity of the film will be extremely poor and it will not exhibit that property, and if it exceeds the upper limit, the adhesive strength will be poor and both will be unacceptable.

The same applies to particle size; in the case of graphite, the particle size is
If it exceeds 60μ, the stability and printability of the etching resist suspension will deteriorate, and sufficient adhesion will not be obtained, which will adversely affect conductivity. This is because if the lower limit is less than 0.1μ, it is usually commercially available and is suitable in view of the viscosity, consistency, printability, etc. of the etching resist suspension. In the case of carbon black powder, the particle size is 0.1μ or less because particles with a particle size exceeding 0.1μ are normally not available, and in the case of carbon black, the particle size is 0.1μ or less because unlike the graphite mentioned above, the particles are chained. This is because it seems that the particles are bonded in a shape, so even if the particles are fine, they are suitable for printability.

(b) As a rubber binder, a polyurethane resin such as Neoprene WRT/WD manufactured by Nippon Polyurethane Co., Ltd.; as a thermoplastic resin binder, a polyester resin such as ESPEL 1300, 1311 manufactured by Hitachi Chemical Co., Ltd.; As the thermosetting resin binder, phenolic resins such as PA-301 and PA-320 manufactured by Sumitomo Decorez Co., Ltd. can be used.

However, if the quantity of the rubber-based, thermoplastic resin-based, or thermosetting resin-based binder is limited, that is, below the lower limit of 5 to 30% by weight, the dispersion, stability, and printing "glue" of the etching resist suspension will deteriorate. It is bad, has insufficient consistency, and has poor printability, making it unacceptable. If the upper limit is exceeded, the consistency is too high, which worsens the printability, significantly deteriorates the conductivity, and causes the property to be lost.

To prepare the suspension for etching resist described above, the above composition raw materials (a), (b), and (c) are mixed in predetermined amounts (a+b+c), dissolved, and dispersed to have a specific gravity of 0.9 to 1.5 and a viscosity of 0.9 to 1.5. Prepare an etching resist suspension of 150 to 10,000 poise. In this case, the apparent specific gravity of the etching resist suspension produced is 0.9.
If it is less than 1.5, the conductivity will be poor due to the lack of fine powder components of graphite and carbon black, and if it is more than 1.5, the dispersion of the liquid will be poor, stability will be lost, and the adhesive force will be poor, so it is not acceptable. The same applies to the viscosity, and if it is less than the above lower limit, printability will deteriorate,
Moreover, if the upper limit is exceeded, the dispersibility of the liquid will be poor and printability will be affected, so it is not acceptable.

Next, using this etching resist suspension, desired patterns of contacts 13 and circuits 14 as shown in FIGS. 4a and 4b are formed on the copper layer 1 of the copper-deposited flexible polyester substrate 11, respectively.
2 and dry the formed printed surface on the substrate at a temperature of 95 to 150° C. for 5 to 20 minutes [Step (A)].

Next, a liquid such as chloroprene rubber, silicone rubber, flexible epoxy, etc. is further applied to the vicinity of the contact pattern 13 on the film substrate on which the contact 13 and circuit 14 patterns have been formed in the step (A), After printing the desired pattern of the spacer layer 15 using a screen printing method, the temperature is 90 to 180°C.
The spacer layer 15 is formed by drying for 10 to 30 minutes [Step (B)].

At this time, the material to be printed and applied as the spacer 15 is a silicone rubber liquid, such as Toray Silicone manufactured by Toray Silicone Co., Ltd.
SE1700 (white), CY52-037A, etc., chloroprene rubber liquids such as Showa Neoprene Co., Ltd. trade name Neoprene WRT, WD etc., and flexible epoxy resin liquids such as Tau Chemical International Limited trade name DER732 , 741−
A etc. can be used.

The thickness of the spacer layer 15 printed at this time is preferably 50 to 400 μm. The reason for this is that if the film thickness is less than the lower limit, the contact part 13 and the circuit part 14 will be too close to each other, and there is a risk that they will come into contact with each other due to vibrations, twisting of the film, etc. , If the upper limit is exceeded, when attempting to make contact at will, the film thickness is large, making it difficult to make contact unless a relatively large pressing force is used.
This is not possible because the pressing force causes local deformation of the film. The spacer print coating layer 15 within the above range is suitable for sufficiently functioning as a keyboard switch.

Next, the copper-deposited film substrate 11 on which the spacers 15 were formed in the step (B) was heated with 5 to 50 Baume ferric chloride (FeCl ₃ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ) and chloride. Etching is performed using a cuprous (CuCl) solution to dissolve the copper exposed on the surface of the substrate 11 (see Figures 6a and 6b), and after washing with water, the etching is performed at a temperature of 60 to 100°C for 30 minutes. Dry for 1 hour [Step (C)].

Thus, ferric chloride (FeCl ₃ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ and cuprous chloride (CuCl)
If the specific gravity of the etching solution is less than 5 Baume, it will take a long time to dissolve the copper exposed on the surface, which will reduce the efficiency of the process.
If it exceeds Baume, the solubility of copper will be too fast and it will corrode the edges of the lower copper layer of the contacts and circuit patterns, so it is not possible. For these reasons, the optimum specific gravity of the etching solution is 5 to 50 Baumé.

Next, copper etching is performed in this etching step (C), and a notch 17 is made between the contact portion and spacer portion of the obtained desired pattern and the circuit portion for folding the two portions in half and overlapping them. It is formed on the film substrate 16 [Step (D)].

In other words, regarding the board in which the printed circuit board of the contact and spacer section and the printed circuit board of the circuit section are integrated, it is necessary to fold it in half and stack it on top of each other, so be sure to make a cut 1 at the folded part.
7 (see Figures 7a and 7b).
If the notch 17 is not provided, the printed circuit board 16 cannot be reliably folded in half, which may cause contact failure when used as a keyboard switch. The length of the cut 17 is preferably within a range of 50 to 95% of the folded length of the printed circuit board 16. If it is less than the lower limit, the film cannot be sufficiently folded and overlapped. If the upper limit is exceeded, the printing of the conductive wire connecting the contact portion Co and the circuit portion Ci may become too thin, which may cause printing defects or disconnection, so it is not possible.

Finally, the film substrate 16 is folded along the notch 17, and the contact portion and spacer portion Co and the circuit portion Ci are overlapped and opposed to each other as partially shown in FIG. Process (E)].

In this case, as shown in FIGS. 7a and 7b, positioning holes 18 are drilled at desired positions of the film substrate 16, and the contacts and spacer portions Co and the circuit portions Ci are connected to each other. It is also possible to perform positioning accurately and easily.

As described above, the manufacturing method according to the present invention (A+B+C
+D+E) This concludes the detailed explanation of each step. The main points will be explained below with reference to the drawings.

For example, as shown in FIGS. 4a and 4b, the etching resist suspension is used in step (A) on a flexible polyester film substrate 11 having a thickness of 50 to 125 μm and having a copper vapor deposition thickness of 0.2 to 1.0 μm. As shown in FIGS. 5a and 5b, spacers 15 are printed and applied near the periphery of the contact pattern in step (B), as shown in FIGS. 6a and 6.
As shown in Figure b, etching is performed in step (C) to complete the patterns of the contacts, spacer parts, and circuit part. Next, as shown in FIGS. 7a and 7b, cutouts 17 are made in the board, and the board is folded in half as shown in FIG. The thin keyboard switch member is completed.

Examples will be further described in detail below.

Example 1 (a) 30% by weight of graphite powder with a particle size of 0.1 to 60μ and particle size
A conductive suspension for etching resist consisting of 15% by weight of carbon black of 0.1μ or less, (b) 25% by weight of a polyurethane resin, namely Paraprene 22S, trade name of Nippon Polyurethane Co., Ltd., and (C) 30% by weight of isophorone. Using paint (a+b+c), as shown in FIGS. 4a and 4b, a desired pattern in which the contacts 13 and the circuit portion 14 are integrated is formed by screen printing to a thickness of 0.3 μm in copper vapor deposition.
It was printed on a 100 μm polyester film substrate 11 and dried at a temperature of 110° C. for 10 minutes (step (A)). Next, in the vicinity of the contact pattern of the copper-deposited polyester film substrate 11 on which the contact points 13 and the circuit pattern 14 were formed in this step A, a silicone rubber liquid, namely Toray Silicone SE1700 (trade name, manufactured by Toray Silicone Co., Ltd.) (white) and CY52−
A desired spacer pattern 15 was printed by screen printing using 037A and dried at 150° C. for 10 minutes. In this case, the thickness of the silicone rubber coating film of the spacer 15 is 125μ (Step B) (Step 5a).
(see Figure and Figure 5b). Next, the exposed surface of the flexible printed circuit board 11 was etched with copper using a 35 Baume ferric chloride (FeCl ₃ ) solution, unnecessary copper was dissolved, washed with water, and dried at a temperature of 80° C. for 45 minutes ( Step C) (see Figures 6a and 6b). Next, the contact 13 and spacer layer 15 portion (i.e. contact Co) obtained in the etching step (C) and the circuit 14 portion (i.e. circuit portion Ci)
A cut 17 for folding and overlapping both parts Co and Ci was formed in the film substrate 11 to about 90% of the folded length (step D) (see FIGS. 7a and 7b). Finally, the notch 17
The film substrate 11 was folded in half along the line, and the contact portion Co and the circuit portion Ci were overlapped and faced to each other (step E) (see FIG. 8).

The printed circuit board obtained at this time, that is, a thin keyboard switch member on which spacers 15 were printed, completed the contact 13 and circuit 14 patterns, and the silicone rubber coating film as the spacer 15 showed sufficient elasticity. It has excellent characteristics as a flexible printed circuit board for thin keyboard switches.
It showed sufficient practicality.

In addition, instead of the above polyurethane resin (b), chloroprene rubber, namely the product name Neoprene WRT, WD manufactured by Showa Neoprene Co., Ltd., and polyester resin, namely the product name Espel 1300, manufactured by Hitachi Chemical Co., Ltd.
1311, and phenolic resin (product name PA-301, 320 manufactured by Sumitomo Decores Co., Ltd.), chloroprene (trade name Neoprene WRT manufactured by Showa Neoprene Co., Ltd.) instead of the silicone rubber liquid mentioned above.
WD, and flexible epoxy resin product name manufactured by Dow Chemical International Limited
Almost the same good results were obtained even when using DER732, 741-1A, etc., respectively. In any case, the remarkable effects of the present invention were observed.

Example 2 (a) 30% by weight of graphite powder with a particle size of 0.1 to 60μ and particle size
15% by weight of carbon black powder of 0.1μ or less; (b)
Using a conductive suspension paint for etching resist (a+b+c) consisting of 25% by weight of polyurethane resin, namely Paraprene 25S (trade name, manufactured by Nippon Polyuren Co., Ltd.) and (c) butyl carbitol, as shown in FIGS. 4a and 4b, , contact 13 and circuit 1
Four parts of the desired pattern were printed by screen printing on a 75μ thick polyester film substrate 11 with a copper vapor deposition thickness of 0.3μ, and dried at a temperature of 110°C for 15 minutes (Step A). Next, in the vicinity of the contact pattern 13 of the polyester substrate 11 on which the contact pattern 13 and the circuit pattern 14 have been formed in this step A, a silicone rubber liquid, namely Toray Silicone (trade name, manufactured by Toray Silicone Co., Ltd.) is applied.
Desired spacer pattern 15 by screen printing method using SE1700 (white) and CY52-037A
was printed and dried at 150°C for 10 minutes. In this case, the thickness of the silicone rubber coating on the spacer 15 is
150μ (Step B) (see Figures 5a and 5b). Next, this flexible printed circuit board 11 is copper-etched using a 35 Baume ferric chloride (FeCl ₃ ) solution to dissolve unnecessary copper, and washed with water at 80°C and 45°C.
(Step C) (see Figures 6a and 6b). Next, a cut 17 is made between the contact point 13 and the part Co of the spacer layer 15 obtained in the etching step (C) and the circuit part Ci by folding and overlapping the two parts Co and Ci to the length. Approximately 70% of
The above steps were formed on the film substrate 11 (Step D) (see FIGS. 7a and 7b). Finally, the film substrate 11 was folded in half along the notch 17, and the contact portion Co and the circuit portion Ci were overlapped and opposed to each other (step E) (see FIG. 8). In the flexible printed circuit board obtained at this time, that is, the thin keyboard switch member on which the spacer 15 is printed, the silicone rubber coating film as the spacer 15 exhibits sufficient elasticity and becomes a cushion, which is sufficient for use as a thin keyboard switch. It showed great practicality.

In addition, instead of the polyurethane resin (b) above, chloroprene rubber, namely the product name Neoprene WRT and WD manufactured by Showa Neoprene Co., Ltd., and polyester resin, namely the product name Espel manufactured by Hitachi Chemical Co., Ltd.
1300, 1311 and phenolic resin, namely PA-301, 320 manufactured by Sumitomo Decorez Co., Ltd., and chloroprene, ie, neoprene manufactured by Showa Neoprene Co., Ltd., in place of the silicone rubber liquid.
Similar good results were obtained using WRT, WD, and a flexible epoxy, DER732, 741-A, manufactured by Dow Chemical International Limited. In any case, remarkable effects of the present invention were observed.

Note that in this second embodiment, the contact point 13
When the pattern portions of the circuit 14 and the circuit 14 are separated and formed on separate substrates 11 (for example, the pattern portion 5a
In Figures 1 and 5b, contact 13 and spacer layer 1
5 is shown as one, and the circuit section that should be opposed to it is not shown. ) Figures 7a and 7b
As shown in the figure, holes 18 for overlapping are formed on both substrates 1.
1 can be drilled in advance. This overlapping hole 18 allows the contact portion Co and the circuit portion Ci to be accurately opposed to each other.

[Brief explanation of drawings]

Fig. 1 is a schematic plan view showing an example of a gold-plated circuit part of a copper-clad laminate for a conventional keyboard switch, Fig. 2 is an enlarged schematic cross-sectional view of a conventional keyboard switch member, and Fig. 3 is a schematic diagram of a conventional keyboard switch. FIG. 4a is a perspective view showing an example of a film for a spacer of a member, and FIG.
A perspective view showing a copper-deposited polyester film substrate with contact parts and circuit parts obtained in the process printed on the surface thereof, and Fig. 4b is a line A-B of Fig. 4a.
FIG. 5a is a schematic perspective view of the substrate showing the spacer layer printed around the contact points in step B, and FIG. 5b is a schematic enlarged cross-sectional view taken along line A-B in FIG. 5a. FIG. 6a is a schematic perspective view of the film substrate 16 after copper etching in step C, and FIG.
Fig. 7a is an enlarged schematic cross-sectional view taken along the line A-B in Fig. 7a, Fig. 7a is a schematic perspective view of the substrate with incisions made in step D, and Fig. 7b is a schematic diagram of A in Fig. 7a.
- an enlarged schematic cross-sectional view thereof taken along line B;
Furthermore, Fig. 8 shows the contact part Co and the circuit part Ci in the E process.
FIG. 2 is an enlarged schematic cross-sectional view of the case where it is folded using a notch. DESCRIPTION OF SYMBOLS 11...Copper vapor deposited film substrate, 12...Copper layer of film substrate 11, 13...Contact pattern, 14
... Circuit pattern, 15 ... Spacer layer, 16
...Insulating film substrate, 17...Notch, 18
...Overlapping hole, Co...Contact part, Ci...
Circuit section.

Claims (1)

[Scope of Claims] 1 (a) 20 to 80% by weight of a mixed fine powder of graphite powder with a particle size of 0.1 to 60μ and carbon black powder with a particle size of 0.1μ or less, (b) polyurethane resin, chloroprene rubber,
5 to 30% by weight of a rubber, thermoplastic and thermosetting resin binder consisting of one or more of polyester resins and phenolic resins, and (c) dimethylformamide, diethyl carbitol, ethyl carbitol, isophorone and turpentine. Solvents such as oil 15~
A suspension with an apparent specific gravity of 0.9 to 1.5 and a viscosity of 150 to 10,000 poise is used as a conductive paint for etching and resist, and is used as a flexible copper-deposited polyester. A step (A) of printing desired contact and circuit patterns on a film substrate using a screen printing method and drying; a spacer layer forming step (B) in which a desired spacer layer pattern is printed using a screen printing method using a liquid such as chloroprene rubber, silicone rubber, flexible epoxy, etc., and dried; The copper vapor-deposited film substrate obtained in (B) was mixed with ferric chloride (FeCl ₃ ) having a specific gravity of 5 to 50 Baume, and ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ).
and an etching step (C) in which copper is etched on the exposed surface using various solutions such as cuprous chloride (CuCl), washed with water, and then dried; Forming a cut in the film substrate between the contact point and spacer part of the pattern and the circuit part to fold and overlap both parts.
(D) and step (E) of folding the film substrate along the cut so that the contact portion and spacer portion and the circuit portion overlap and face each other (A+B+C+D+E). A method for manufacturing a flexible thin keyboard switch member having a spacer printed thereon.