JPS5857920B2 - printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that a conductor pattern made of copper foil is formed on one side of an electrically insulating layer made of adhesive, and circuits such as resistors, dielectrics, conductors (coils, jumper wires), etc. are formed on the other side. A flexible sheet on which an element is printed and a flat non-flexible substrate are bonded together facing each other, the printed circuit element is placed between the non-flexible substrate and the flexible sheet, and the printed circuit element is placed between the non-flexible substrate and the flexible sheet. The present invention relates to a printed circuit board configured to connect circuit elements exposed on the flexible sheet to conductor patterns exposed on the flexible sheet via through-hole connection conductors.

Conventionally, circuit elements such as resistors and dielectrics are printed on one insulating surface of a printed wiring board and connected to a copper conductor via a silver powder-resin conductor, or the copper conductor is directly connected to the circuit. A circuit element is printed to be used as an electrode of the element, and sometimes the circuit element is printed across another conductor via an insulating layer, which is called a cross-over, and a silver powder-resin conductor is printed on another copper conductor. There was an example of connecting with

However, the above-mentioned 1. The second method reduces the wiring area of the copper foil conductor and reduces the area where printed wiring can be placed, which is extremely uneconomical. The need to additionally print an insulating resin layer between the crossed-over conductors increases man-hours, and the insulation properties of this insulating layer drop rapidly in high humidity, often leading to short circuits, reducing reliability. It had the disadvantage of losing .

The present invention provides a printed circuit board that overcomes these conventional drawbacks.

Hereinafter, the printed circuit board of the present invention will be explained with reference to drawings of embodiments.

When manufacturing the printed circuit board of the present invention, first, a flexible sheet is prepared, in which a conductive pattern made of copper foil is formed on one side, and circuit elements such as resistors, dielectrics, and conductors are formed on the other side; Prepare a non-flexible substrate to be bonded.

To prepare a flexible sheet, the first step is to apply thermosetting resin adhesive 2 made of a mixture of epoxy resin and polybucdiene resin several times on the back side of copper foil 1 as shown in Figure 1, and then heat it. 140℃, 30℃ for curing
The adhesive layer 2 is semi-cured to a B stain state under conditions of 10 minutes.

That is, a sheet is created in which the adhesive layer 2 is lined with the copper foil 1.

Here, if the adhesive layer 2 is completely cured to the C slige state, cracks will easily occur in the backed copper foil 1 layer, so here the adhesive layer 2 is cured to the B slige state. Just do it.

In the cured state of B Stino, it has a certain degree of flexibility, and the adhesive 2 forms an insulating resin layer.

Next, as a second step, circuit elements such as a resistor 3, a conductor 4, a dielectric 5, etc. are printed on the flexible resin layer 2, as shown in FIG.

The resistor is carbon powder-phenol resin resistance paint, the conductor is silver powder-epoxy resin conductor paint,
As the dielectric material, polysulfone resin, barium titanate powder-epoxy resin dielectric paint, etc. are used.

These circuit elements are screen printed on the resin layer 2 and cured at 120-150 degrees for 30-60 minutes.
Let it be the impedance value of a predetermined circuit element.

At this time, the adhesive layer 2 is heated again, but the degree of curing does not reach C stain.

Each of the circuit elements may be adjusted by additional printing or cutting in order to correct the impedance value after the resin is cured.

Next, in the third step, as shown in FIG. 3, a through hole 6 is formed as a passage for electrical connection between the circuit element or its electrode conductor and the copper foil surface.

The thickness of the copper foil 1 of the flexible sheet is 0.0101
rlJn ~ 0.11nJ11, and the thickness of the adhesive layer 2 lining is 0.05111JII ~ 0.1712J, and punching work of this thickness requires preheating, etc.
It is extremely economical because it does not require a large-sized punch press and can be achieved with equipment such as a paper tape punching device.

On the other hand, as the fourth stage, as shown in Fig.
A non-flexible substrate 7 having a soldering heat resistance of seconds and a thermosetting adhesive layer 8 formed on one side is prepared.

The adhesive layer 8 may be either a C-stino cured adhesive or a B-Stino cured adhesive.

Then, the adhesive layer lined with the copper foil of the flexible sheet, that is, the circuit element printed surface and the surface of the adhesive layer 8 of the non-flexible board 7 are opposed to each other at an angle of 160 to 180 degrees as shown in FIG. G30 to 60 minutes, 9 to 20 to 40
They are bonded and integrated under pressure and heating conditions of /crA.

At this time, since each circuit element also contains an adhesive resin component, it is possible to bond them together at the same time.

Sometimes, if necessary, a partial overcoat of resin may be applied to some or all of the circuit elements.

In this fourth step, the adhesive layer 2 and the paper-based phenolic resin laminate 7 are bonded, and the adhesive layer 2 has a through hole 6 penetrating the copper foil layer 1 and the adhesive layer 2, and A printed circuit board is completed in which circuit elements 3.4.5 are installed between 2 and the laminated board 7.

Then, as shown in FIG. 6, the holes 6 previously drilled in the copper foil layer 1 and the adhesive layer 2 are printed with a silver powder-resin conductor paint 9, so that the copper foil layer 1 and the circuit elements 3. 5 is electrically connected.

The depth of the hole 6 is 0.010 to 0.1711. , it is easy to print the silver powder-resin conductor paint over two layers.

As shown in FIG. 6, a solder resist 10 is printed on the printed portion of the silver powder-resin conductive paint in the hole so that it is not exposed to the solder bath.

As the solder resist resin, it is desirable to use an epoxy resin containing an organic inhibitor to suppress silver migration.

It goes without saying that the copper foil 1 is formed into an arbitrary conductive pattern by printing a known etching resist and removing unnecessary portions of the copper foil, and this is done after the first stage is completed.

In such a configuration, when forming printed circuit elements to be internally mounted on a conventional synthetic resin printed wiring board, an expensive insulating layer is used, such as a multilayer board structure in which boards on which circuit elements are printed are laminated. There is no need to use an epoxy resin or polyimide resin as a glass cloth base material, and unlike when using a relatively inexpensive polyester or polycarbonate film as an insulating layer, it does not soften and deform in a general solder bath (260° CIO seconds). There are no drawbacks.

As described above, according to the present invention, an adhesive is applied to the back side of a copper foil, and an adhesive electrical insulating sheet having a copper foil conductor pattern on the back side is used, and a resistor and a dielectric are placed on the electrical insulating sheet. Since a circuit element film is formed on the substrate, etc., and the circuit element film is internally placed between the non-flexible substrate, the degree of freedom in arranging the circuit elements is increased, and the wiring density of the exposed conductor pattern can be improved. It is possible.

Further, since a flexible sheet having a circuit element film and a non-flexible substrate are bonded together, the number of man-hours is significantly reduced, and the method has a significant effect in terms of manufacturing.

[Brief explanation of the drawing]

The drawings show an example of the structure of the printed circuit board of the present invention, and FIGS.
FIG. 6 is an explanatory diagram showing the manufacturing process. 1... Copper foil, 2... Adhesive layer, 3...
...Resistor film, 4...Conductor film, 5...
...Dielectric film, 6...Through hole, 7...Non-flexible substrate, 8...Adhesive layer, 9...
...Conductor paint, 10...Solder resist.

Claims (1)

[Claims] 1 A flexible sheet having a conductor pattern made of copper foil is adhered to the surface of a non-flexible substrate on an electrical insulating layer formed as a B-stage cured film of an adhesive, and the electrical insulating layer constituting the non-flexible substrate and the flexible sheet is A circuit element film such as a resistor film, a dielectric film, a conductor film, etc. formed in A printed circuit board characterized by electrical connections.