JPS5940319B2 - flexible printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible printed wiring board, in which dimensional deformation due to shrinkage of the flexible base material is significantly reduced.

The element body of the flexible printed wiring board is, for example, as shown in FIG. 1, a flexible base material 1 consisting of a band-shaped body made of a flexible synthetic resin such as polyester or polyimide and having a thickness of about 0.012 to 0.3 mm. It is manufactured by bonding strip-shaped conductive foils 2 and 3 on both sides using pressure rollers 4 and 5 under appropriate conditions such as pressure, temperature, and adhesive. In this case, the flexible base material 1 is always T-shaped so as not to sag.
Tension is applied with a force of , and therefore the flexible base material 1 of the manufactured element body is in a state of being stretched in its longitudinal direction. After that, the conductive foils 2 and 3 of the element body manufactured in this way are sequentially formed into a circuit conductive foil 6 by etching or the like, as shown in FIG. After cutting, a flexible printed wiring board is constructed as shown in FIG. When forming the circuit conductive foil 6 on the substrate, a required circuit configuration is performed.

By the way, assuming that the conductive foil 6 for circuit is formed only on one side, the conductive foil 6 for circuit is formed with a conductive foil 6 for circuit extending in a direction perpendicular to the longitudinal direction A of the flexible substrate 1, as shown in FIG. When a large number of foils 6 are concentrated, since the base material 1 is originally stretched in the longitudinal direction A, each circuit conductive foil 6
Contraction occurs between the holes, and this contraction causes deflection and distortion, changing the set dimension Lo of the base material 1 to Li (however, L0>L1), for example, shortening the interval between the mounting holes T, etc. When installing the electronic device into a device, a situation occurs where the mounting position of the electronic device does not match.

Note that such dimensional deformation occurs even when the circuit conductive foil 6 is formed on both sides, and if a large number of circuit conductive foils are provided in the same direction on both sides, the flexible base material shrinks and the dimensions similarly change. Variations occur.

The present invention significantly alleviates these conventional drawbacks, and one embodiment thereof will be described below with reference to FIG. 4.

In FIG. 4, the same parts as in the conventional structure of FIG. 3 are given the same numbers, and the present invention
A circuit conductive foil 6 is provided on the back side of the circuit conductive foil 6 in the same manner as the circuit conductive foil 6 on the front side, and the direction of alignment of the circuit conductive foil 6' on the back side is generally set relative to the alignment direction of the circuit conductive foil 6 on the front side. It is constructed so that it intersects when viewed.

By forming the alignment directions of the circuit conductive foils 6 and 6' on the front and back sides of the flexible base material 1 in a direction that completely intersects the front and back sides, for example, the flexible base material 1 can be formed between the circuit conductive foils 6 on the front side. Even if the material 1 tries to shrink, it is prevented by the circuit conductive foil 6' on the back side, and conversely, shrinkage of the flexible base material 1 between the circuit conductive foils 6' on the back side is prevented by the circuit conductive foil 6 on the front side. Therefore, shrinkage of the flexible base material 1 as a whole hardly occurs, and in particular, the shrinkage in the longitudinal direction A is maintained substantially at LO.

Therefore, the mounting hole 7 provided in the flexible base material 1
The dimensions between the two are almost the same as the settings, allowing for efficient mounting work on electronic equipment. In addition, in the above embodiment, the conductive foil for the circuit is also provided on the back side, but this does not necessarily have to be for the circuit, and even if it is a conductive foil that does not constitute a circuit, The same applies to a mixture of foil and conductive foil that does not constitute a circuit.

In addition, if the conductive foil for circuits on the front side is aligned partially or in different directions, the conductive foil on the back side should be arranged so that the conductive foils on the back side intersect partially or in each section according to the alignment direction of the conductive foil on the front side. do it. As described above, the present invention is a thin flexible substrate having a conductive foil for circuits formed on its surface, and a conductive foil is provided on the back side of the thin flexible base material so as to intersect with the conductive foil for circuits on the front surface. This has the great effect that dimensional deformation due to shrinkage of the material is significantly reduced and a flexible printed wiring board with good dimensional accuracy can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of crushing the material of a flexible printed wiring board, Figure 2 is a diagram showing the process of sequentially forming a flexible printed wiring board from that material, and Figure 3 is a diagram showing a conventional flexible printed wiring board. Top view, FIG. 4 is a top view showing one embodiment of the present invention. 1...Flexible base material, 6,6'...
・Conductive foil for circuits.

Claims (1)

[Claims] 1 A conductive foil for circuits is formed on the surface of a flexible base material made of flexible synthetic resin such as polyester or polyimide and has a thickness of 0.3 mm or less, and a conductive foil for circuits on the surface is formed on the back side of the flexible base material. A conductive foil is provided so as to intersect with the foil, and the conductive foil on the back side is formed from a mixture of a conductive foil for circuits and a conductive foil that does not constitute a circuit, and the shrinkage rate is made small by the conductive foils on the front and back sides crossed. A flexible printed wiring board featuring: