JPS61176184A - Continuity structure of double-side flexible circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Industrial Field of Application" The present invention is directed to forming, for example, a tunnel-shaped opening at a conductive location on both the front and back circuit patterns without using a conventional through-hole conduction means. Accordingly, the present invention relates to a conductive structure of a double-sided flexible circuit board that allows easy soldering to provide required electrical conduction between front and back circuit patterns at low cost and reliably.

``Prior Art'' As shown in FIG.
A substrate material such as a so-called flexible double-sided steel-clad laminate is prepared, and through-holes 8 are first drilled in this substrate material toward the conductive points, and then on the entire surfaces of both sides and on the inner peripheral surface of the through-holes 8. After forming through-hole plating 9,
It is common to construct circuit patterns 6 and 7 on the front and back sides which are subjected to through-hole conduction treatment through a photo-etching process.

"Problems to be Solved by the Invention" In the through-hole conductive structure as described above, the through-hole plating process is complicated, and in the photo-etching process for forming double-sided circuit patterns, the existing through-holes 8 and There is a need for a solution to this problem, which is a major bottleneck in improving the manufacturing efficiency and cost efficiency of this type of double-sided flexible circuit board. On the other hand, according to such a through-hole conduction method, unnecessary through-hole plating is uniformly formed on circuit pattern parts other than conductive points, which tends to reduce the flexibility of this type of circuit board. Therefore, for products that require high flexibility, it is necessary to add a special process to prevent through-hole plating from adhering to circuit patterns other than through-hole conductive parts, which increases product cost. There is the inconvenience of doing so.

``Means for Solving the Problems'' The present invention departs from the conventional through-hole conduction method and provides a simple cut-out treatment at the conduction point, thereby achieving high efficiency and low cost in the soldering process. This provides a conductive structure for a 7-lexiple circuit board. Therefore, in a double-sided flexible circuit board in which required circuit patterns made of conductive foil are provided on both sides of a flexible insulating base sheet, the present invention provides for example A cut-out portion having a partial cut such as a tunnel shape is provided, and solder is applied to the cut-out portion to electrically connect both the front and back circuit patterns.

According to such a conductive structure of a double-sided flexible circuit board, compared to the conventional through-hole conductive means, it is possible to achieve a significant reduction in the number of steps and contribute to a reduction in the cost of the product. Further, the conductive structure according to the present invention has the advantage that it is possible to obtain electrically and mechanically strong and reliable structure, and also to maintain the flexibility of this type of circuit board optimally. .

"Embodiment" FIGS. 1 and 2 show a conceptual perspective view of essential parts and a sectional configuration diagram thereof for explaining the conduction structure of a double-sided flexible circuit board constructed according to an embodiment of the present invention. , 1 indicates a flexible insulating base sheet commonly used for this type of flexible circuit board, 2 indicates a front circuit pattern obtained by etching a conductive foil, etc., and 3 indicates a similar back circuit pattern. As shown in the figure, a protruding opening 4 having a substantially tunnel-like shape is formed at a portion where the front and back circuit patterns 2 and 3 match each other. The opening portion 4 is made by forming a common notch in both circuit patterns 2 and 3 from either side of the circuit patterns 2 and 3 using an appropriate plunging jig, etc. as shown in FIGS. 2 and 3. As shown, it is possible to configure the front and back circuit pattern portions 2A, 3A in the raised portions and the other flat front and back circuit patterns 2, 3 in a continuous state. The shape of the incision and protrusion 4 is not limited to a substantially tunnel-like shape as shown in the figure, but may have an optimal shape depending on the shape or fineness of the circuit patterns 2 and 3, such as a mountain shape or a rectangular protrusion shape. It can be adopted arbitrarily, and therefore, the shape of the circuit pattern 2° 3 at the portion constituting the cut-out portion 4 is not limited to the conventional land pattern shape, and the straight portions of both circuit patterns 2 and 3 or It is also possible to adopt a mode in which a part of the curved portion is used in combination.

When hand soldering or 7-mer soldering is applied to the above-mentioned cut-out raised portions 4 formed as means for making the circuit patterns 2 and 3 conductive on both the front and back sides, the cut-out raised portions 4 are formed as shown in FIG. Sufficient solder 5 flows into the cavity, and the raised circuit pattern portions 2A and 3A are reliably and firmly electrically connected to the other circuit patterns 2 and 3 on the front and back sides, and a dip soldering method or the like is adopted. In this case, as shown in FIG. 5, it is possible to obtain a more reliable connection state. In such a connection process using solder 5, the two circuit pattern parts 3A and the other two flat circuit patterns 2 and 3 at opening #154 are connected in succession as shown in FIG. As a result, heat conduction during soldering is uniform to each part, and it is therefore possible to obtain a solder adhesion structure that is extremely good both electrically and mechanically. However, although not shown in the drawings, the structure of the incision 4 may be a discontinuous protruding structure instead of the continuous tunnel-shaped structure as described above, and the conductive structure may be substantially the same even if the soldering process is performed. You can also get

The conduction structure of the double-sided flexible circuit board as described above is
Prepare a required flexible double-sided steel-clad laminate, etc., and form desired circuit patterns 2 and 3 on both the front and back sides using a conventional photo-etching method, etc., and then remove the conductive portions and form the circuit patterns 2 and 3. This can be easily and efficiently carried out by performing a surface coating treatment using insulating ink or a cover film, etc., and then performing a step of forming the cut and raised portion 4 as shown in the figure and a solder connection treatment step. (1) A significant reduction in the number of processes can be achieved without using the conventional through-hole conduction process.

(2) Since it has a conductive structure between both the front and back circuit patterns, it is possible to ensure a strong and stable connection state electrically and mechanically.

(3) As a solder connection method, 70-solder or dipping means can be adopted in conjunction with the structure of the cut and raised portion to promote high-speed solder connection.

(Since the required conduction structure can be provided only at the necessary locations of both the front and back circuit patterns, the original flexibility of the circuit board can be maintained well.

(5) Since it can be applied to extremely fine circuit patterns, it also contributes to higher density of circuit boards.

(6) It is easy to visually check the continuity part, and
Maintenance is also easy.

(7) Products of excellent quality can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view conceptually showing the conduction structure of a double-sided flexible circuit board constructed based on an embodiment of the present invention. FIG. 3 is an enlarged sectional configuration diagram, FIG. 3 is a sectional configuration diagram taken along the line A-A in FIG. 2, and FIG. 4 and FIG. FIG. 6 is a cross-sectional explanatory view conceptually showing a conventional through-hole conduction structure. 1: Insulating base sheet 2 2: Front circuit pattern 3: Back circuit pattern 4: Cut-out portion 5: Connection solder Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a double-sided flexible circuit board in which required circuit patterns made of conductive foil are provided on both sides of a flexible insulating base sheet, it is necessary to electrically conduct the front circuit pattern and the back circuit pattern. A double-sided flexible circuit board characterized in that a cut-out portion having a partial notch is provided at a location, and solder is attached to the cut-out portion to electrically connect both the front and back circuit patterns. conductive structure.