JPH0632360B2 - Double-sided connection type flexible circuit board manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a flexible circuit board, and more particularly to a structure in which circuit parts can be connected to both sides of the circuit board by adopting a pre-punch method. The present invention relates to a method for manufacturing a double-sided connection type flexible circuit board which is advantageous when applied to.

"Prior Art" This type of flexible circuit board is generally constructed by forming a required circuit pattern on one surface of a suitable base film material with a conductive foil such as copper foil. However, as the packaging density of circuit components increases, as shown in FIG. 2, a form is used in which the circuit components 20 and 21 are mounted and connected to both surfaces of the flexible circuit board 10 of one layer. In such a double-sided connection type flexible circuit board 10, required circuit patterns 15, 16, 17 and 18 and the like are formed on the base material 11 via the adhesive layer 12 by a photoetching method and the like, and are formed on the upper surface thereof. A surface protective layer 13 such as a cover film is provided via the adhesive layer 12, and in this example, the circuit patterns 16 and 17 are configured so that the circuit component 21 can be connected from the back surface by adopting a pre-punch method, and other circuit components can be connected. 20 is connected from the surface to the circuit patterns 15 and 18 as usual. Then, it is possible to provide the back surface side connection portion 14 and the front surface side connection portion 19 with the outside by a similar method.

The flexible circuit board 10 as described above includes the circuit components 20, 2
Since 1 is mounted and connected from both sides, solder heat resistance and adhesive strength to the circuit pattern are required more than other general flexible circuit boards. The manufacturing method as shown in FIG. 3 is adopted for the flexible circuit board.

That is, first, an adhesive layer 2 is provided on a suitable base material 1 as shown in FIG. 1A, a pre-punch 3 for backside connection is appropriately provided as shown in FIG. 2B, and then soldering is performed on both surfaces. Rough surfaces 22A and 2 obtained by heat resistance treatment and adhesion strength improvement treatment
A conductive foil 22 such as a copper foil having 2B is laminated on the base material 1 via the adhesive layer 2 as shown in FIG. 3 (3), and then the resist material 5 is filled in the pre-punch holes 3 and then the conductive foil 22 is formed. Then, a photoresist material 23 is applied as shown in FIG.
6 can be appropriately formed as shown in FIG. 5 (5), and finally the surface protection layer as described above can be provided on the circuit pattern to complete the series of steps. Since part of the back surface of the circuit pattern 25 is exposed in the pre-punch hole 3 by removing the filling resist material 5, connection from the back surface side is possible.

"Problems to be Solved by the Invention" In such a manufacturing method, however, the rough surfaces 22A and 22B provided on both surfaces of the conductive foil 22 necessary to secure solder heat resistance and adhesive strength are In the pattern forming step, the presence of the rough surface 22A causes various problems.

That is, it is difficult to apply the photoresist material 23 uniformly due to the rough surface 22A, and the degree of forming air pockets on the surface 22A is high.
No. 4, 25, 26, etc. are caused, and foreign matters such as dust are easily attached to such a rough surface 22A, and it is difficult to remove the attached foreign matters. As a result, it becomes a cause of defective circuit patterns, and as a result, it is difficult to improve the yield.

"Means for Solving Problems" The present invention is a double-sided connection method using a pre-punching means capable of achieving good circuit patterning processing without causing defects while achieving the solder heat resistance and adhesive strength improving processing as described above. It is an object of the present invention to provide a preferable method for manufacturing a flexible circuit board. Therefore, according to the present invention, after the required pre-punching process for the base material, the adhesive strength and the adhesive strength are only applied to the joint surface with the base material. A conductive foil that has been subjected to solder heat resistance improvement treatment is joined to the base material, and after the required circuit pattern has been formed on the conductive foil having a smooth surface, the exposed surface of the circuit pattern has improved adhesion strength and solder heat resistance improvement treatment. After applying
It is configured to form a surface protective layer.

"Embodiment" FIG. 1 is a process drawing of a method for manufacturing a double-sided connection type flexible circuit board according to an embodiment of the present invention, and the same reference numerals as those in FIG. 3 represent the same elements as those, In the step of forming the pre-punched holes 3 in the base material 1 provided with the adhesive layer 2 as shown in FIG. 1A, and the conductive foil 4 laminating process after the resist material 5 is filled in the holes 3 in FIG. 2B. Is a smooth surface 4 with a rough surface 4B only on the joint surface on the base material 1 side as shown in FIG.
After using the conductive foil 4 of A and uniformly coating the photoresist material 6 on the smooth surface 4A, the required photo-etching treatment for the conductive foil 4 and the peeling treatment of the resist material 6 are performed as shown in FIG. Required circuit pattern 41,
42, 43, etc. are appropriately formed. Since the circuit patterning process is performed in the state of the smooth surface 4A of the conductive foil 4 as described above, it becomes easy to completely perform the foreign matter removal processing such as dust necessary for the surface 4A, and as in the conventional case. It is possible to smoothly end such a step while preventing an undesirable situation such as air accumulation.

After such a circuit patterning process, the filling resist material 5 is removed and the pre-punch holes 3 are filled with, for example, the circuit pattern 4.
2 is exposed or the resist material 5 is filled as it is so as to be removed in the final step, and as shown in FIG. 5 (5), the smooth exposed surface of each circuit pattern 41, 42, 43 has solder heat resistance and After the rough surface 7 for improving the adhesive strength is appropriately formed, a surface protection layer 9 such as a cover film is provided on the circuit pattern surface via the adhesive layer 8 as shown in FIG. Can be finished efficiently.

Here, the rough surface 7 for improving solder heat resistance and adhesive strength
Is formed by dissolving a chromium-based rust preventive solution in water and immersing the copper foil in the solution to form a deposited film on the surface of the copper foil.

[Advantages of the Invention] According to the method for manufacturing a double-sided connection type flexible circuit board according to the present invention, the base material is subjected to the treatment for improving the adhesive strength with the surface protection layer and the solder heat resistance after the required circuit pattern forming step. Since it is configured to be performed separately from the side, in the photoresist material coating process for the conductive foil, it is possible to suitably prevent foreign matter such as dust from entering or the occurrence of a circuit pattern defect due to air retention as in the conventional method, and it is excellent in high yield. There is an advantage that the double-sided connection type flexible circuit board adopting the pre-punching method of high quality can be efficiently manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a double-sided connection type flexible circuit board according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining an example of mounting circuit components on the double-sided connection type flexible circuit board of this type. FIG. 3 is a drawing, and FIG. 3 is a manufacturing process drawing of a double-sided connection type flexible circuit board by a conventional method. 1: Base material 2: Adhesive layer 3: Pre-punched hole 4: Conductive foil 4A: Smooth surface 4B: Coarse surface 5: Resist material 6: Photoresist material 7: Coarse surface 8: Adhesive layer 9: Surface protective layers 41 to 43: Circuit pattern

Claims (1)

[Claims] 1. A method for manufacturing a flexible circuit board by a pre-punch method, which allows circuit components to be connected to both surfaces of a circuit board, wherein a surface to be joined to the base material is subjected to a required pre-punching process. Only by bonding a conductive foil that has been subjected to a treatment for improving adhesive strength and solder heat resistance to the base material, apply a photoresist material to the surface of the conductive foil, and perform the required photoetching treatment for patterning. A double-sided connection type characterized in that after forming a required circuit pattern for the conductive foil, the exposed surface of the circuit pattern is subjected to a treatment for improving adhesive strength and solder heat resistance, and then a surface protective layer is formed. Flexible circuit board manufacturing method.