JPH0416034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a printed wiring board on which a printed resistance is formed.

[Conventional plate technology]

Conventionally, thick film circuits in which printed resistors are formed between adjacent wiring layers on a substrate and lead frames for external connection are provided at the ends of the substrate have been used in various fields.

[Problem that the invention seeks to solve]

However, such conventional circuits require a lead frame, which increases the number of parts and requires man-hours for assembling the lead frame, resulting in poor economic efficiency.

[Means for solving problems]

In order to solve these drawbacks, the present invention reinforces a flexible substrate with a reinforcing plate and forms a printed resistor in the reinforced portion.

[Effect]

The wiring layer provided on the flexible substrate acts as it is as an external connection line.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, 1 is a reinforcing plate made of hard material;
2 is a flexible printed circuit board having a portion extending outward from the end of the reinforcing plate 1, and this flexible printed circuit board includes a flexible base film 2a, an adhesive layer 2b, and a flexible printed circuit board bonded to the adhesive layer 2b. It is composed of a wiring layer 2c. 3 is an underlay layer formed to reach from one side of the adjacent wiring layer 2c to the other, 4a and 4b are silver electrodes formed on the wiring layer 2c, and 5 is an adjacent predetermined electrode 4.
A printed resistor 6 is formed on the underlay layer 3 to connect between a and 4b, and an overlay layer 6 is formed to cover the printed resistor 5. The reinforcing plate 1 is bonded to the surface of the flexible printed circuit board 2 opposite to the surface on which the wiring layer 2c is formed via the adhesive layer 1a, and is attached to the underlay layer 3, the electrode plates 4a and 4b, and the printed resistor 5. , the overlay layer 6 is formed in the region reinforced by the reinforcing plate 1.

A printed wiring board having such a configuration is formed as follows. First, the first layer 2 of the base film 2a
After transferring and adhering the wiring layer 2c to b by a method such as a high-speed transfer method, the adhesive layer 1a of the reinforcing plate 1 is adhered to the opposite side of the base film 2a by a method such as a hot press. After printing, drying and curing the underlay layer 3, the silver electrode 4a,
4b is printed, dried and cured. Next, a carbon-containing paste is printed by screen printing or the like, dried and hardened to form the printed resistor 5, and then an overlay layer 6 is printed, dried and hardened, and then trimmed by a method such as laser trimming. Do this.

Since the printed wiring board thus formed has the wiring layer 2c and the printed resistor 5 formed on the flexible printed circuit board, the wiring layer 2c of the flexible printed circuit board can be used as it is for external connection, which is not necessary in the past. This eliminates the need for a lead frame, which was previously required.

FIG. 2 shows an example in which the overlay layer 6 is formed of an overlay film. If you do this,
Since the overlay layer 6 can be formed by simply pasting an overlay film, the steps of printing, drying, and curing can be omitted.

In the process of manufacturing the printed wiring board constructed as described above, the printed resistor 5 is trimmed last, so that the overlay layer 6 is partially damaged during trimming. Damage to the overlay layer 6 due to trimming is of an extremely narrow width, so it hardly poses a problem in practice, but damage to the overlay layer 6 becomes a problem when moisture resistance stability of the resistance value is strictly required. In such a case, as shown in FIG. 3, a top coat 7 can be formed to cover the trimmed portion or the entire top surface of the flexible printed circuit board 2 by adhering a film or applying silicone resin. Good.

Note that in the above embodiments, the underlay layer 3
need only be formed on the portion where the printed resistor 5 is formed, and the overlay layer 6 may be formed not only on the portion where the printed resistor 5 is formed but also on the entire surface. Further, the underlay layer 3 and the overlay layer 6 are formed of the same material.
The area reinforced by the reinforcing plate 1 can be used to mount not only printed resistors but also chip parts such as chip capacitors.

〔Effect of the invention〕

As explained above, in this invention, a printed resistor is formed in a region where a flexible printed circuit board is reinforced with a reinforcing plate, and the flexible printed circuit board is made to extend outward from the reinforcing plate. The layer can be used as it is for external connection, eliminating the need for a conventionally required lead frame, thereby eliminating the cost of lead frame parts and assembling man-hours, which has the effect of improving economic efficiency.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the invention, and FIGS. 2 and 3 are sectional views showing other embodiments. DESCRIPTION OF SYMBOLS 1... Reinforcement plate, 2... Flexible printed circuit board, 2a... Base film, 1a, 2b... Adhesive layer, 2c... Wiring layer, 3... Underlay layer, 4
a, 4b...Silver electrode, 5...Printed resistor, 6...Overlay layer, 7...Top coat.

Claims (1)

[Claims] 1. A reinforcing plate, a flexible base film having a reinforcing plate bonded to one side and a portion extending outward from the end of the reinforcing plate, and a reinforcing plate on the other side of the base film. first and second wiring layers connected adjacent to each other in the plate-reinforced area;
From the first electrode of the underlay layer formed to reach from the first wiring layer to the second wiring layer, and the first and second electrodes provided in the first and second wiring layers, respectively. A printed wiring board formed of a printed resistor formed on an underlay layer to reach a second electrode, and an overlay layer formed to cover the printed resistor.